Why did Kylo Ren think he was any match for Luke after he saw Luke survive the AT-AT bombardment? And why was Poe worried about Luke facing Kylo "by himself"?
THIS IS NOT MEANT TO BE A CRITICISM OF THE FILM. THIS IS JUST ABOUT THE CHARACTERS.
He watches Luke bombarded by a dozen AT-ATs at max power...and then sees Luke walk out without a scratch from the whole thing. Yes, Luke was a projection but Kylo didn't know that, and even if he had, a Luke who can project himself across the galaxy is going to be extremely powerful (Rian Johnson said it was one of the most impressive Force feats in the franchise, which Ren would have known too) and on top of that projection Luke could physically interact with the world as he did when he kissed Leia on the head so he could have killed Kylo if he wanted. Anyways back to what Ren did know - he sees Luke walking out of a bombardment of AT-ATs effortlessly unscathed. Surely he doesn't think he could do the same thing? So why does he even think of facing him rather than ordering his forces to flee from the guy more powerful than them all?
And Poe watches all of this and is still concerned about Luke facing Kylo Ren by himself. While his care is adorable I would also think he'd think that after Luke handled the entire First Order on his own, that Kylo wouldn't be that big a deal. So why was he still worried? Did he also think Kylo was more powerful than Luke?