It's an easy explanation. In Adams' case he thought Sheffield United was beneath him from the outset, hence his shit attitude and refusal to train properly. That's why he showed only brief flashes of quality. But showed just enough to get noticed.
But that's all I have to say about him. Players mean nothing to me unless they are our employees and we no longer employ him.
Nothing makes me cringe more than reading "good luck to the lad" posts whenever somebody leaves.
Good luck to the lad