I was watching World Championship Wrestling from late 1988. “Dr. Death” Steve Williams was chasing Mike Rotondo for the TV Championship, and then like two weeks later, with no explanation, Williams joined Rotundo and Kevin Sullivan in The Varsity Club. Was there ever a reason provided for this?

This reminded me of a horrible modern day heel turn that the WWE would try to pull off. 

There was a reason!   He literally phoned into the show from a hotel room in Japan one week and announced that he was joining the Varsity Club.  It was the most awesomely lazy turn ever.