Board Thread:The Flash discussions/@comment-9346948-20181205013242/@comment-27700324-20181205154108

The Savitar thing could be explained as him learning of Savitar when Savitar was travelling around, seeking godhood. He couldn't be erased from people's memories since there would be a massive time paradox. That was how Barry and Nora were able to see his death.

With Thawne being in the future, keep in mind that the one from Crisis on Earth-X is still around after he escaped Black Flash putting him in the Speed Force. So he could have fought the Flash after Crisis on Earth-X and then he got caught, being thrown into Iron Heights.