#the other diluc who were alive couldnt stop him

An Interesting Concept…

What if there was a Kaeya who had lost everything? Crepus died and he was blamed for it. Diluc also blamed him and - in the moment he received his Vision - he accidentally killed him. He’s the one who goes on a failed Fatui killing rampage that only makes things worse when he can’t find any of the answers he seeks.

He completely snaps when he sees wanted posters declaring him the murderer of the Ragnvindr Clan and he proceeds to spiral into insanity. He begins to actually believe that everything was truly and utterly his fault. In a fit of desperation to right his wrongs, he uses khemia to create a device that lets him jump between different Teyvats. In each one, he hunts down versions of himself and kills them (whether they’ve turned “evil” or not), having completely convinced himself he’s doing the right thing.

Then he comes to the canon version of Teyvat and starts to seek this world’s version of Kaeya out too. However, even if Kaeya agrees with him, Diluc makes up his mind that he’s not going to fail where all his other alternates have. He’s not going to let his brother die.

Especially not to some psycho alternate version of himself.