I just kinda whipped this up real quick for my thoughts on it. Samurai Jack has to operate on multiple timelines or otherwise it doesn't make sense. The main timeline is represented by A, where it's the standard timeline. Jack and Aku have their battle, Jack almost kills Aku, Aku flings him into the future. There are two timelines created from this, the first being the rest of A, where Aku turns the world into what we see in the show leading up to its climax, and then B, which is the timeline that gets created when Jack and Ashi return to the past moments after Aku sends Jack away.
What I'm thinking is what basically happened is that, after branching off from timeline A, the things
created in A only manage to stick around for a limited amount of time, but because they didn't
come from B they can't continue to exist. You can still remember something, it did exist for as long as it did, but it's not able to stick around.
Probably the most fucked up thing about the show operating like this is that Aku most likely completely curbstomps the entirety of the forces attacking him because the only weapon capable of killing him fucked off to the past.
