I don’t think Carrie’s passing had much to do with it at all. I think Trevorrow couldn’t come up with a version of the story where he could redeem Kylo, and that’s what caused the split. None of his drafts have it, and the Jack Thorne draft that does have it… he probably didn’t want his name on that once he read it, because shortly after it came in, he was gone. Most of the other aspects of the two approaches share similarities (which is probably why Trevorrow got the credit he got, even if Abrams and Terrio really did page one rewrite it) but the only really big difference is Kylo.
I do believe the wedge issue was Lucasfilm execs believed this story needed to have the redemption of its bad guy, and the writer/director they initially hired to deliver that ending didn’t feel the same way. The guy they got to replace Trevorrow not only would do it, but he’d resurrect Carrie Fisher in order to get it done. Oh, and he ALSO directed the biggest domestic earner of all time, whereas the other guy just made Book of Henry.
That probably seemed like a pretty brilliant move in September 2017.