Kylo was already planning to break and keep Poe for good after he was first captured, and planted a series of mental commands/Jedi mind tricks/whatever to ensure that Poe would find his way back to him even if he was rescued.


Cue Poe, safely back at the Resistance, slowly being consumed by a horrifyingly increasing sex drive and vivid dreams and thoughts of Kylo using him as his pet, until he's unable to fixate on anything else. He knows exactly what's happening and is disgusted and terrified, but can't bring himself to confide in anyone when it's taking all his willpower not to fly directly into the First Order and prostrate himself.