User blog comment:Eobard95/Savitar's timeline/@comment-27673963-20170918021317/@comment-26624146-20170919094853

Savitar changed the timeline because of 2056-Barry (as I said before you made me remember the one hole in my theory I forgot to add was that 2056-Barry must've known who he was). After 2056-Barry learned who Savitar was he sent a message to Rip Hunter in 2016 hoping he could change things, which I think meant either stopping Savitar's existence or killing 2016-Barry when he returned for the Dominator invasion which Rip was present for in 2056-Barry's timeline.

However because Eobard Thawne and Rex Tyler altered the timeline Rip vanished so he wasn't around to do anything about Savitar. Instead Stein and Jax shared the message with Barry which prompted him to look at the 2024 newspaper and see that Iris West-Allen had been replaced by Julie Greer. Since the version of Savitar imprisoned in the Speed Force who'd lived through the events of 2020 but hadn't killed Iris in 2017, and therefore had no knowledge of his actions in 2056, remembers everything 2016-Barry does at that point so he would have inherited Barry's new memories of getting some insight into Iris' uncertain fate.

Since this was an event Savitar never lived through, as his timeline is 2056-Barry's timeline, Rip would have been present for the Dominator invasion and wouldn't of had a secet message meaning Savitar never got any insight into Iris' fate whereas Barry himself now did. Because of this he probably grew fearful that things wouldn't play as they should and started working towards having Tracy Brand build the Speed Force trap but still worked towards killing Iris as a backup plan if only to buy himself more time.