Why leave college? Could not afford it, did not enjoy it, thought more could be accomplished outside of it, etc.

There are many reasons beyond just weak character for why someone would not go to college and it's not up to you as an employer to make that judgement call on someone's personality until you've dissected their real reasons for leaving.

This is something that takes a lot of time, way longer than an interview has to offer, so it's best to not make assumptions.