#3 WrestleMania is much more watchable over two nights
One of the biggest positives of a two-night WrestleMania comes from a fan's view. Simply put, the Show of Shows is so much more watchable over two nights. Earlier editions of WrestleMania never used to cross four hours, with the runtime constantly increasing in the late 2010s.
Four hours became five, along with the addition of a two-hour Kickoff Show. As a result, fans get fatigued from watching too much wrestling. This particularly hampered WrestleMania 35. The crowd was barely into the main event of the show, which saw Becky Lynch defeat Ronda Rousey and Charlotte Flair.
It was a shame, but the problem can forever be avoided. The two-night format allows WWE to give the main portion of WrestleMania a combined runtime of up to seven hours, without affecting the fans. Spreading the action across two nights makes the event much more palatable.
It's likely the case most fans would rather watch two three-hour shows with seven to eight matches each, instead of one five-hour show with twelve matches on it. WrestleMania is truly too big for one night.