Craig Hansen wasn't screwed up, he just wasnt that good. He had plenty of chances. At no point in 95 game pitching career did he look like he belonged, and his mechanics were terrible to boot.
Plenty of players are brought up too early and then find themselves, just look at Roy Halladay. Cla Meredith gave up a grandslam and lost his first decision in relief and he went on to be productive for a couple seasons at least.
If Craig Hansen was screwed up because he lacked mental toughness, then he was never going to succeed to begin with.