>>79508854I do not know much about the "old" extended universe, and I don't know if this theory as already been proposed and debunked, but hear me out:
Kylo Ren does not want to be Dark Side, but he has been convinced that he have to, for the greater good, by Snoke.
How was he convinced? What if they partially recycled the Vong idea?
The Emperor knew of this menace, Vader knew (but his feelings for his son had the better of him) and they were convinced that the only way to survive this coming conflict was through the power of the imperial navy and the violence of the Dark Side.
Snoke know of this (we will eventually discover how) and convinces Kylo to sacrifice everything he holds dear for the sake of the entire galaxy: his family, his ideals, his goodness.
Luke knows to, but refuses to believe and he secludes himself on a distant planet, trying to find a solution to the problem that does not involve the Dark Side.
Also, another thought: maybe the outside-the-galaxy threat is attracted by the Light Side, and only an overwhelming presence of Dark Side can keep the galaxy safe; cue Luke going in exile and lowering his power level to zero.
