The following is mash up of a few DM’s:
Luke didn’t do anything crazy. He was clinging to someone in Winter House in an attempt to remain on the cast/relevant for Summer House as it’s known he hasn’t had a storyline since Hannah. That person felt uncomfortable. Nothing terrible transpired. We may see him leave the house for a night but it was just alcohol and a cool off, he didn’t do something terrible that got him fired. It was because he didn’t bring it and that was the final straw.