Well, alright, if you're going to look at it that way. Actually what was Kylo Ren's official position under Snoke anyway? He and General Hux seemed to have equal authority, and indeed, Hux was hesitant to follow Kylo's lead after Snoke was killed until Kylo bitch-slapped him into submission with the Force.
The red guards were a bunch of silent mooks who's only function was to stand there looking menacing and then die in a highly entertaining fashion. By not using the Knights of Ren in their stead, RJ has left the door open for something interesting and worthwhile to be done with them in Episode IX. In short: the Knights of Ren would have been wasted in TLJ.
I must have been getting them mixed up with the alleged jedi students that Ben allegedly took with him.
Who's to say Ben is their leader, though he almost certainly is. "Ren" is probably like "Darth" and all the Knights adopt that as part of their super secret evil bad guy names. For all we know, Snoke just liked to keep his enemy's nephews close and the real head honcho is the yet to be revealed Slagathor Ren.
What he actually says is: "Master of the Knights of Ren..." That could be taken either way, honestly. I mean, if you replace the words "Knight of Ren" with "Jedi Order" then it's clearly a reference to rank and achievement, not absolute leadership. But if you replace it with "Sith Order", then it's definitely the latter. The main problem is that we don't even know what the Knights of Ren are. They could be a group Kylo formed himself under Snoke's tutelage from Luke's surviving pupils, or the remnants of what was once the Imperial Inquisitorius, or they could be an ancient order that have been kicking around in the unknown regions since before the Jedi first came to Ach-To.
Rian was expecting too much from the audience to piece together the hiccups. When I rewatch this weekend, I'll be writing down scenes. I've brought up Chewie and the Porg in the past, but that one is way too easy for anyone to headcanon easy and viable solutions. Other scenes, not so much... As for Luke and the map, someone needs to tell critics that these chapters are part of a larger arc and that more long-hanging fruit would be that while Luke wanted to hide away, somebody planted a map to lead to him. Who might do it and why, like a much bigger trap. Seems pretty compelling to me... Then comes stuff like teleporting items via Force Chats. That I groaned over in the theater at the time, that was simply dismal. Even Leia's force pull wasn't as cringe inducing. And I suppose the point of the pointless scene showing Kylo's horse mane hair with his scarred chest was to show off the massive light saber scar he got from her in "The Farce Awakens". The scar on his face and going down his neck was more than adequate, to remind us of her harming him, how dare the movie flaunt heterosexuality since he was disrobed while talking to Rey... Luke didn't go shirtless for his new fake arm while Leia looked on and hoping to get another tongue-wrestling match in... but that was written long before ROTJ where she states she always knew he was her brother, despite the number of times she was tongue-bathing his tonsils to begin with in ANH and TESB... Remember when Han in ANH states "that escape was way too easy", Rian may have been trying a variation of the theme regarding DJ and why he had all the convenient escape plans... unless he was staying put, knowing he as one person really could not make a difference and escape on his own. Works either way.
Hate to say it and hope I'm wrong, but the whole 'Knights of Ren' thing seems to be a plot artifact from TFA that is going nowhere and TPTB probably wish they could retcon out.
We'll see them. The next film will probably jump ahead to a time after Princess Leia has passed away, where the Knights of Ren are doing battle with the Knights of Rey for the fate of the galaxy. Or some crap like that.
In all honesty, it would not surprise me in the slightest if Episode IX contains no reference to the Knights of Ren at all.
Given that Abrams is at the helm once again there will probably be plot points in the TFA that are brought back up again.
If they junk the Knights of Ren I could see them doing a comic book or novel to explain their absence or their fates.