Honest question: What did he do (or lay the groundwork for) that would have made this happen?
Well, Mr. Bethune was already on the Piedmont property when the buyout occurred. Bill Howard was CEO, but he was getting up in years and it was tacitly acknowledged that Bethune was being groomed to take the lead when Howard retired. At the time of the merger, Bethune was (I think) executive vice president for operations. And before the actual merger was completed, I think (I'm really not too sure about this) he was president of Piedmont for a short time (as Piedmont's leadership began departing the scene.)
When it was clear that Colodny was going to name "Deer-in-the-headlights" Schofield as his successor, Bethune went to Boeing realizing that his future did not bode well any longer at the merged carrier. What the rest of us didn't realize is that our collective futures did not bode well at the merged carrier, either.
Meantime, Lorenzo et al. were doing a number on the PeoplExpress-TexasAir-NYAir-Continental company. It was pretty much a basket case when Bethune was asked to take the helm. With is strong, charismatic and knowledgeable leadership, Bethune managed to turn that carrier completely around into one of the premier carriers of the world.
My own opinion is that, given the great strength and relative health of the US-PS-PI combination at the start, Bethune would have had an unbelievable opportunity to build a powerhouse carrier on what was then a very strong foundation. All we needed in the late 1980's/early 1990's was some strong leadership and vision. We went without any of that for most of the 1990's while other carriers came in and ate away at our business. We never really responded with any "plan," and consistently turned tail and ran whenever challenged. IMHO, Bethune would have been able to respond to any threat proactively, rather than with the reactive leadership we have been saddled with from 1988 to this day.
It's really impossible to know what "might have been." But given Bethune's undeniable track record for successfully running a major international carrier and the fact that he was ALREADY employed here, I cannot help but think that USAir would now rule the world had he been chosen to succeed Colodny.