Board Thread:General Discussion/@comment-34260455-20180118013149/@comment-28802873-20180119171932

This is a wild theory, but maybe No Watch Vilgax is dead or in a state where he's unable to do anything (maybe it has something to do with No Watch Max losing his arm). So having another Vilgax (Prime) over doesn't do much since the first one (No Watch) is in bad shape or dead, it's as good as having only one healthy/alive Vilgax.

I think the Bomb was set to destroy every universe (except No Watch since he's in it) AND every version of Ben with an Omnitrix (whether or not they're Ben, or a relative or a genetical copy) in No Watch's universe, wiping out every "Ben" in every circumstances. Vilgax being out of his universe and not wielding an Omnitrix is what protected him from his bomb's effects.

Also, if I'm not wrong, what fixed the timelines was giving Prime Ben his Omnitrix, so here's another theory: there was originally an Omnitrix in No Watch Ben's timeline, but it got destroyed after getting to its purposed owner, Max (who lost his arm to Vilgax in the process). The events in No Watch would be exactly the same until the Omnitrix arrives, the only difference being who gets it. So No Watch Ben going back to the past was him going to his own past, and by changing it, he turned his past into the Main Timeline's past, creating, or rather, re-creating another timeline where he got the watch instead (the one we all know and love), which fixed the time streams.

So that's it.