Here's what happened:
He was a big fish in a small pond when he was in high school. Being in that position gives way to a sense of entitlement for some folks. So, when he came to Nebraska where he was a big fish in a bigger pond coupled with the sense of entitlement that being a big fish in a small pond gave him, he thought he didn't have to work as hard in practice to get that starting spot. Well, that's not how Bo runs his program, and that's not how Barney runs his offensive line. When he didn't get his starting position, instead of deciding to work harder he decided to say "to heck with this, I don't have to put up with this crap," and left.
He left to a place where he is a big fish in an even bigger pond. Unless the coaching staff at Florida treats him differently than the coaching staff at Nebraska did (which was by no means incorrect), he's going to transfer again to a smaller school where he can be a big fish in a small pond again.
It's like this:
Most of us would rather be a top lawyer in a small firm who makes $100,000 instead of an average lawyer in a big firm who makes $150,000 but knows that the people at the top make $250,000.