Bret Hart is an egomaniacal son of a bitch. In my book, there are two possibilites in this whole screwjob thing.
1. Vince, despairly looking for a way of getting the belt out of Bret before Raw, of the huge risk that Bret didn't showed up and appeared at Nitro and embarrased the belt, found in HHH, a man looking for approval since he lost it for that MSG incident, and HHH suggested the screwjob, HBK happily say another title reign so didn't object and what happened is history.
2. Bret, HBK, Vince and Earl all knew what was happening, and it was an all win situation. Vince gets out the title of Bret saving his company, HBK becomes one more time the face of the company, Earl gets in history as the most well known ref in history, and Bret goes down as the eternal, biggest sympathetic babyface of all industry