Give the Klingon Empire a regent and then it would make sense...they haven't had an Emperor in about two hundred years.
Sort of like the way "Mirror Cartman" on South Park was the good Cartman (since our universe's Cartman is the evil one).
It seemed to me that the point of declaring war on the Federation was to serve as a rallying point for uniting the 24 houses. Without a common enemy (the Federation), the Klingon houses would continue to bicker amongst themselves and remain separate. With a common enemy, the 24 houses may see fit to work together. T'Kuvma wanted to give the other Klingons a reason to unite around him, and the reason was the war.
It's a funny thing, this Light of Kahless. Somebody built it a long time ago ("centuries", says Burnham). Probably not Kahless, whose top construction project seems to have been the first sword. If it was built to summon Klingons to war, has it? I mean, before this? It would be odd for somebody to build the thing and then not make immediate use of it. But if the Light has been lit before, why doesn't T'Kumva mention this? And why hasn't it been noticed? Humans have been able to observe lights in the sky with some precision for "centuries", and Klingons aren't exactly in the farthest reaches of the galaxy. Heck, even if some previous warmonger flipped the switch in 1732 or thereabouts, odds are that the signal would have reached Earth by the 20th century even at lightspeed. And it seemed to make quite an impact on Klingons located lightyears away, so either the light had a FTL component to it, or then there were observers from many Houses in the immediate vicinity, forwarding the news with their FTL radios. Or then T'Kumva just pointed his webcam at the light and transmitted that, but this would be a bit of a letdown... Considering Klingons love to rewrite their history, it wouldn't really surprise me if this is the thirteenth activation of the Light already. We never learned whether it "burned out" or was just "shut down", now did we? Timo Saloniemi
The Klingons in STD are an "empire" the same way Japan was an "empire" during the Sengoku period. I wish they would have given just a little explanation as to what, exactly, made the Light of Kahless something special and worth paying attention to. It seems like any old schmoe could come along and activate it whenever they wanted to. Or does it only respond to someone wearing this extremely rare torchbearer armor? Do you have to pass a series of impossible tests to be able to activate it? Kor
....Are there several, sown along the borders of the ancient realm so that they can be lit like signal bonfires of yore when the enemy approaches? Are these things even Klingon? Or something the Klingons found, made by their betters for uses they cannot comprehend? Why was T'Kumva's private little Light only partially cloaked, rather than entirely or not at all? Because the thing came with a distorting property (rather than a full cloak) attached, or because its properties disrupted the cloak that T'Kumva installed? It would be fun to learn more about this, and about where T'Kumva got his cloak. The current set of writers may have little desire to return to the double pilot, done largely by their predecessors, but later seasons might see some of the stuff explored even if Klingons cease to be a major presence. Tying loose ends is a favorite pastime of late-seasons writers in modern Trek... Timo Saloniemi
You're assuming that the previous Klingon empire had the same society and values as the current. What little we do know of Khaless right now comes from the religious fanatics of T'Kuvma's sect and the various self-serving fables we saw in TNG. "Savage Curtain" implies he was a military genius and also a gifted mimic, while the stories told by Future Alexander make him out to be a kind of warrior philosopher. It's just as likely that Khaless was the first Klingon explorer whose mission and motives weren't totally different from Starfleet's, that he created the beacons at the outer edge of Klingon space to warn them of the approach of invaders, and that for most of his reign he expanded Klingon power and influence by dominating other races politically, intellectually and culturally rather than militarily. Channeling Klingon passion into constructive pursuits would make them a true force to be reconned with; it is always easier to destroy than create, but Klingons never do anything half-assed, so the things the create promise to be pretty epic. Well, the beacon evidently only shines until someone comes and answers the call. On Earth that would have been, what, twelve hours? Long enough for astronomers to notice a new star in the sky but short enough that when they try to verify it with subsequent observations, suddenly there's nothing there, and it gets written off as a false positive. It's a religious icon, you really just have to volunteer. And also, probably, know how to throw the switches that activate it (I doubt it has an instruction manual carved into the sides). Of course, the original torchbearer's next of kin doubted whether or not the other houses would even show up to answer the beacon, which suggests its not really relevant as a military or political tool, it's just an ancient relic that most Klingons know about, even if they don't revere it or give a shit about it. Put another way: even atheists understand what "baptism" means. And in Arab countries, you don't have to be a practicing Muslim to understand the significance of the Temple Mount. In this case, it's like some lunatic climbing on top of the Western Wall and launching a bunch of signal flares out of the helmet of a dead Israeli soldier. That is, if nothing else, a rallying cry for a war that a lot of people were probably already hoping for.
I didn't have much issue with the rest of what you said, as most of it can be explained. The above is a bit odd. You would think the federation would have sent a ship to look for survivors at least. That itself would have provided enough focus on the situation to want to get the cloaking tech. The Klingons not getting it? Who knows...maybe they initially felt it was't honorable to sneak around invisible or something.
Now there's a cool idea. One just wonders why Klingons of the 2250s through 2370s persuasion would wish to rewrite this particular thing about their history, turning a heroic and influential Kahless into a clown who spends his time wrestling with his kid brother... The speed at which the Houses responded is a mystery to begin with. Those "centuries" ago, lighting the thing might have been followed by years of waiting for something to happen - for a warp 1.9 conquest cruiser to arrive, for the folks back home to amass their armies, whatever. And turning the beacon off before this was achieved might be the ultimate letdown, precluding its effectiveness in ever summoning anything again. But the survivors (Sary, Georgiou's telescope, what-have-you) would already have fled to Federation space, bringing the news of there being no more survivors. And thanks to the Binaries massacre, the Klingon side appeared to be winning at this early stage - the battlefield would probably be a no-go area for Starfleet. Yes, Starfleet would know about the invisibility screens, through explicit eyewitnesses such as Saru. But it turns out Starfleet would have little reason to care, because the secret of cloaking died with T'Kumva, and (as we later learn) none of the other Klingon factions made any use of it in the early war. All the Klingons who saw the cloak in action died at the Binaries, or became stranded along with Voq's faction - otherwise, Voq himself would not have been stranded there, but would have been helped out by surviving allies. In contrast, the Klingons who got out did so before they learned about cloaks. Kol's faction did not take part in the fight, and did not believe in invisibility screens. And either Voq was too proud to try and bribe rescuers with the secret of cloaking, or he was cut off from the rest of the Empire altogether (we never hear of him being able to communicate his plight, or even his continued survival, to anybody) - so even with the war turning against the Klingons, Kol would have little motivation to return to the Binaries. But when he did, in desperation, he came specifically to look for this semi-mythical invisibility device he himself only grudgingly believed in. Timo Saloniemi