Не слух/спойлер, а скорее теория: рыцари Рена - бывшие ученики Люка, все дружно убежавшие к Сноуку. И Люка повергло в уныние не то, что он не смог обучить племянника, а то, что он потерпел глобальное поражение - все (или почти все) его ученики переметнулись на другую сторону.

Эту теорию уже опровергли

Выглядит логично. В плане объяснения того, что Люк сдался. Да и в РВ не было такого, чтоб массово кто-то уходил на тёмную сторону. Ну разве что в много-лет-дбя такое могло быть

He met her eyes steadily. "We've lost our son, forever." Leia bit her lower lip, refusing to concede. "No. It was Snoke." Han drew back slightly. "Snoke?"

She nodded. "He knew our child would be strong with the Force. That he was born with equal potential for good or evil."

"You knew this from the beginning? Why didn't you tell me?"

She sighed. "Many reasons. I was hoping that I was wrong, that it wasn't true. I hoped I could sway him, turn him away from the dark side, without having to involve you."

[SNIP]

"I thought I could shield him from Snoke's influence and you from what was happening."

[SNIP]

He had trouble believing what he was hearing. "So Snoke was watching our son."

"Always," she told him. "From the shadows, in the beginning, even before I realized what was happening, he was manipulating everything, pulling our son toward the dark side."