Thor lost 95% of everything in his life. His mom, dad, his brother, his homeland, all his friends minus Sif who’s missing, and 75% of his people. So yes, I can see that happening to Thor.
Just as the video game makers of Injustice saw Superman going totalitarian after being tricked to kill Lois Lane, his unborn child and nuking Metropolis.
Didn’t you watch the movie, he came to that revelation after talking to his past mom, and getting out of his funk. Especially after helping bring the snapped people back.
Offscreen in Infinity War, it was Valkyrie who led the survivors from Thanos and eventually reconnected with Thor on Earth. She helped the Asgardians settle in Tonsberg, while Thor was there King-in-name-only feeling sorry for himself.
He’s protecting his people by going off with the Guardians, the same way he was between the Dark World and the beginning of Ragnarok, going off on quests and stopping dangers.
Valkyrie doesn’t need mentoring from him, she’s two generations older than him, remember.