Why wouldn't the proper coaching help professional wrestlers become main eventers?
When I say "proper coaching," this is exactly what I mean:
First, think rationally of what professional wrestling is supposed to be and the correct person to represent it. For example, if professional wrestling is supposed to portray people beating the crap out of each other until they win while participating in brutal matches, it's logical to imply that the toughest looking dudes on the roster have the most potential to represent the company.
Second, uncover what the fans want to see. This could be done in many ways such as through surveys and could be done secretly or obviously. It's wise to do this secretly and cleverly to avoid possible spoilers.
Third, coach the wrestlers desired to be faces of the company in accordance to what fans want to see based on the survey results. For example, if fans want more technical wrestling, coach your face of the business into adding technical wrestling to his style.
Fourth, provide your wrestler with an entertaining gimmick based on what the fans want to see based on survey results and improve your wrestler's mic skills accordingly. How to be great on the mic could be learned by watching or learning from other great entertainers.
Fifth, build these wrestlers up and eventually put them in the main event. If done correctly, the proper coaching should be foolproof because you would have promoted exactly what most of the fans wanted to see.
This applies to jobbers with potential, not people already successful in the main event.
Feel free to pick apart any statement you disagree with in a kind manner and refute it.