#1. The main event
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Even though Brock Lesnar's title reign has been boring for the fans, WWE views it as something humongous. Thus WWE may not want the Universal title to change hands on any other instances than the main event.
Since WWE has already announced that the main event of Wrestlemania 35 would be the RAW Women's championship match between the Champion Ronda Rousey, Smackdown LIVE Women's champion Charlotte Flair, and the 2019 Women's Royal Rumble winner Becky Lynch, the Universal Title match will be pushed down the card.
Thus WWE may be reluctant to put Seth Rollins over Brock Lesnar at the Showcase of the Immortals.
The points mentioned above are solidified even more with the latest rumors surrounding Brock Lesnar and his appearance at the WWE event in Saudi Arabia later this year. Putting all pieces of the puzzle together, we should not be surprised if the Beast pins the Architect clean at Wrestlemania 35.
Major rumor about recently released stars HERE