Complex sentence: As Hart was the champion, WWF owner Vince McMahon devised the Montreal Screwjob, secretly changing the planned outcome of a title match, which resulted in Hart losing the title in an unfair manner.
Split into simpler sentences: As Hart was the champion, WWF Owner Vince McMahon devised the Montreal Screwjob, secretly changing the planned outcome of a title match. This resulted in Hart losing the title in an unfair manner.