Like holy shit, all of a sudden, it’s like a rush over me that is reconnecting the dots between the events of the past and the Luke we get in TLJ. Ben Solo at the time was a risk/threat to Luke’s new Jedi Academy. This Academy meant so much to Luke, it’s what his masters would be proud of and the burden he had on his shoulders to make it happen. The moment one single student would burn it, he had a moment where he snaps, hence the moment where he ignites the lightsaber in Kylo’s hut. But the passive Luke we know was always there because as he said, he immediately regretted it. It wasn’t only his mistake of freaking out Ben Solo at the time that made Kylo Ren, it was his huge narrow mindset that his sole purpose, especially as a legend, was to rebuild a Jedi Order once again from scratch.
But since he failed that, that was it, he felt overwhelmed. He let his masters down (so he thought), he let Han and Leia down, he failed Ben Solo, and he let the galaxy down. The galaxy has no room for legends that can’t live up to the burden bestowed on Luke.
I know I’m restating what most of these posters in this thread have been trying to get into my thick skull, but idk, it just clicked for me finally whenever darthrush dropped that comment about how Luke losing his raison d’etre logically leads to the loss of faith Luke we eventually get.
I also saw the flashback moment as Luke seeing things like his close friends dying too (Han). It wasn’t just the academy. It was his friends and the galactic state. Someone on here compared it to Luke having the chance to kill baby hitler and that’s a good way of putting it. He let his deep down flaws take a hold of him and what he had foreseen in that moment and he realized that he failed his apprentice. The coincidence of Ben waking up and the whole situation just led everything to the tragedy that happened and Luke felt like a complete failure to everyone around him.