Yeah, it was probably just an attempt at Gowron's life that missed & got one of his men instead. The whole notion of K'empec choosing to have a Starfleet captain mediate would surely have sat poorly with the Duras clan & their Romulan supporters, which is why K'empec did it. He knew a delay, which involved Starfleet, & Picard to boot, would very likely draw out more foul play from the assassin, which I have to assume he already suspected was Duras, given the family history... a history unknown to Gowron nor anyone else, besides K'empec, Worf & Picard.
K'empec being poisoned is also an assassin method that doesn't frequently happen by Klingons. It too rings of Romulan involvement. So you're K'empec, & some underhanded swine kills you with poison, like a Romulan, & Duras, who is secretly known to have family links to Romulans is conspicuously vying to be your replacement. Your best play is to throw some curveballs that frustrate him, & see if he bites. He did.
Using a Romulan bomb would be a fine way to implicate Duras; using it so that assuredly only worthless goons die would be a good ploy from Gowron, then, pointing the finger at Duras and highlighting how Romulans are no good for the Empire.
That's an unbelievable bunch of duplicity for a Klingon who isn't Duras, & how would he get a Romulan bomb? It's a really thin theory imho
And Gowron was the one with a motivation to poison K'Mpec, while Duras would only have benefited from the old bastard's continuing rule and the protection this offered to his House and the shady deals with the Romulans.
Not true. K'empec is certainly not a fan of hiding Duras' family dishonor. He only did so to prevent the entire empire from crumbling, which could very well be a temporary fix. As long as K'empec is alive, that secret can surface, if ever he wants to do the honorable thing. Even Duras moments before Worf kills him, makes the claim that now that K'empec is dead, only he (Duras) is able to clear his name now
Plus, if he can successfully grab the throne, then he can kill the secret unquestionably. Nah... it's some pretty savvy Romulan chicanery going on.... & it took involving Picard to keep it from going tits up imho lol