#2. To set-up a Fatal-4-way at WrestleMania 36
WrestleMania has always been an event where the company tries to get every superstar possible on the card. Unless they're injured or are held back for creative reasons, battle royales and multi-person matches are usually the way of getting as many names on the card.
That's why in the last few years we've seen multi-man tag team title matches, United States title matches, Intercontinental title matches and more. Given that WrestleMania is also the time that they have nothing creatively for Braun Strowman, it likely makes sense for them to put him in a match that isn't very important in the bigger picture.
A former WWE writer just went after JBL for his comments HERE
Moreover, his presence would add to the match and he doesn't need to be pinned to lose, so it doesn't harm him. Sami Zayn vs Shinsuke Nakamura vs Cesaro vs Braun Strowman certainly isn't a bad match on paper and could be a fun one if given the right time. WWE usually does a great job with Fatal-4-Way matches.