#2 The lack of heel challengers for Rollins on RAW
If Rollins wins the Universal Championship, WWE would have a tough time to find a compelling challenger for him.
Rollins has recently fought AJ Styles for the top prize. It'd be desperate to revisit the rivalry so soon. Furthermore, Styles is the United States Champion. WWE would want to give him an extended run with that title.
The next option is Bray Wyatt. However, he will spend time in the mid-card before he wrestles at the top of the mountain.
Elsewhere, Samoa Joe has lost a ton of matches over the last year. His US Championship runs were short. He needs stellar rivalries to make him a thrilling prospect at the top. Also, Bobby Lashley is out with an injury. Drew McIntyre, too, has lost a lot of steam.
On the contrary, Lesnar as the Universal Champion spices things up.