Plans always change in WWE and sometimes late changes are made before the biggest show of the year.
PWInsider is reporting that the original opening match at WrestleMania 35 was supposed to be Randy Orton vs. AJ Styles. As noted on Monday by Dave Meltzer on Wrestling Observer Radio, the Universal Championship match between Brock Lesnar and Seth Rollins was not originally supposed to go on first and even Hulk Hogan had no idea that Paul Heyman would be walking out to the ring during his segment.
PWInsider added that the line-up change happened around 5:30 pm during the Kickoff show as the cruiserweights were in the ring. The change may have been done to accommodate Lesnar so he could fly home immediately after his match so there was some truth to what Heyman said during his promo on Sunday.
Lesnar vs. Rollins was originally supposed to go on right before the main event. Aside from that change, the rest order of the card went as scheduled.