#1 It’s the best time for The Demon King to return
In the past year, we have only seen The Demon King emerge once at SummerSlam 2018 where Balor squashed Baron Corbin in an unexpected way.
Finn Balor won his initial Universal Championship match as The Demon King against Seth Rollins at SummerSlam 2016.
If there is any plan to give Finn Balor an extended match against Lesnar or have him beat Lesnar, then Balor should do so under The Demon King persona to make it much better for the fans and make it more sellable.
Finn Balor is an extremely gifted wrestler and athlete who competes even better when he is under his alter ego persona and going into the Royal Rumble bout as The Demon will surely give fans more reason to believe in him.
If he does win the match and the championship, then he can continue to defend it as The Demon King which will give his reign a whole new perspective which is missing from the previous Universal Championship reigns.