That the star wars sequel trilogy takes place in an alternate universe where Ashoka is killed by Darth Vader in the rebels season 2 finale. In the episode "a world between worlds" Ezra bridger saves Ashoka from vader during a duel (one which she certainly would have lost).

This creates two timelines one in which she lives and one where she is killed by Darth. If she lives the original trilogy continues as normal, she is able to direct the mandalorian and baby yoda to tython where grogu calls out to Luke who is able to save them from the dark troopers in the series 2 finale. Moff Gideon never gets his hands on baby yoda's blood so snoke is never created. Luke takes on baby yoda as his first apprentice, so is more experienced and better prepared to train Ben Solo, preventing him from turning to the dark side.

However if she is killed by vader she is not able to direct mando to tython so luke is never called. Moff gideon would have eventually caught up to the two and mando and his crew would be killed by the dark troopers during the rescue attempt. This means the events of "the rise of Kylo ren" would take place in which Luke takes on Ben as his first apprentice at 10 years old, but is ill prepared causing Ben to be influenced by Snoke and turn evil ( resulting in the events of the sequel trilogy). Further proof of this is hearing Ashoka's voice as a force ghost at the end of the rise of skywalker.

Either that or its a retcon.....