He didn't have a chance to. He reacted, briefly, to the growing Darkness, hesitated, saw his nephew again and was attacked. Afterwards, he saw his school burning and dead students.
I guess I struggle on the other side. Luke faces a crushing defeat of all that he was supposed to create and is supposed to just shake it off and believe the Jedi can continue? How does that make sense? That's...pretty shaky.
We didn’t see the second happen, so I haven’t really talked about that.
Thing is though...Luke is a hero, Hero with the big aitch even (not a typo for once.) Generally they don’t give up and peg it away. It does make you wonder why he left the map if planned on just vanishing for all time and not return if needed.
The old EU had him refusing to hunt down his nephew (who is so transparently the model for Ren, only he had more of a...logical setup.) even, and especially after, he had tried to turn his son into his apprentice and brought about the death of his wife. He didn’t withdraw all together, or give up. So there’s already an interesting comparison out there.
In terms of still canon stuff, and screen stuff, he didn’t give up after finding out Vader was his father, he didn’t give up after getting maimed, and he didn’t give up on Vader or his ideals when he was staring death in its direct-current fingertips. So I can see how it’s difficult to reconcile that with the specifics of his exile. If he had put himself into exile the way Yoda had (essentially waiting until new Jedi sought him out, because if the Jedi totally fall, there’s nothing left to face the Sith, and they don’t have the power to do it alone.) that makes a little more sense. Except we already know that one or two force users and a power base/military is enough to take and hold the Galaxy for a decade or two (Luke and Leia plus the New republic would be a light side analogue to Palpatine and Vader plus the Empire.) só it all gets a bit odd.
It’s all part of the rush to emulate the rebel/empire dynamic. Not treating the First Order as a threat after the republic knows it has Vader’s grandson gone all sith running around with them?
It’s the wobbly foundation underpinning the sequel trilogy betraying it again, but maybe the can give it so,e wiggle room. Mostly we just ignore it until we can’t anymore.
But no...the Luke stuff is a bit wobbly, and it is a bit like we kind of have to accept it, even if we don’t really think it makes a whole lot of sense. There’s a lot of that...admittedly in Star Wars in general...but particularly in the sequel trilogy.