That could very well be, I have no idea, but just because someone's friends aren't involved in sports doesn't mean they're bad influences.
Maybe he grew up with non-sports friends and has a quieter personality that needs some extra outreach to fit in among the rowdy football dude types, so when he had a head coach who was noncommunicative and a position coach who tried the hardass approach on him, he just said "what am I even doing if nobody wants me here?"
Other than a small weed-related ticket, I don't think there was ever any sign that Betts was on a dark path or anything like that, right? I think he just needs the right kind of coach/leader to guide him a little bit, and Rhule seems like the exact right kind of person to do that.