I am not too sure about him becoming a turncoat.
I don't think he's a turncoat either. I had seven paras written on the episode when first review was posted. I deleted them, because it would have been me defending Eugene and Dwight. I didn't want that, but now I think I should have.
Thing about Eugene is that he is more and less like I am. I often see solutions to thinks before they appear. And I am also a coward for not raising arms and being a biggest bully in the room.
In fact, I hide much like my icon, the mechanical spider. I too find games relieving tension rather than building up stress. And I too shy away from social occasions, meeting with people, because i just have been put down too often.
Eugene and Dwight harbour hatred towards Negan. And Dwight's committing a murder of Negan's doctor was an act of war, not something Negan should have ever committed if he'd understood that everyone in his camp are scared to death.
I thought the same - until the moment Eugene pushed in the line and took everything. That was basically Eugene saying "actually, you know what, this ain't too bad, I got the biggest bully around who has my back".
Eugene pushed the line and almost went back at the end of it, until he thought to try something and see if they buy lies. He knows he is valuable to Saviours. And in some respect they are treating him better than Rick's people ever did.
First chance he has, he will flee back to Rick's side. There's no doubt about that. Him and Dwight are prisoners in Yard. And their only duty is to survive. Whatever it takes.