They knew that Al Qaeda was planning on attacking the embassy but didn't do anything about it, . . .
That part of the conspiracy theory has been shot down by the recent "whistleblower" testimony. They testified that Stat Dept. officials were incompetent, but they all agreed that there was no purposeful plan to knowingly allow an attack to occur.
The big kerfuffle seems to be over the claim that more security was asked for well before the attack, but they didn't get more security. I would hazard a guess that many other embassies have requested more security and not received it, but no one has been hurt.
It is just political theater with Republicans seeing if they can get some mud to stick.