Bailey was an idiot. Why not take Potter's offer to run his affairs
given that George runs it his way?
Potter had flat out admitted that Bailey had beaten him and his advisor (or whoever that was in the scene before) admitted Bailey was exceptional at what he did.
Bailey could have made the fortune he had desired (and lost out on after screwing things up with Wainright) and still be able to help the people of Bedford Falls. With a newborn on the way, he should have swallowed his pride and tell Potter (with faux bravado) that next morning that he would take his offer.
Instead he let his temper get the best of him (which seems to be his biggest flaw)
Uncle Billy's biggest flaw was being a drunken buffoon.
Mother is the name for God on the lips & hearts of all children -Eric D. Raven