He is called Umarak the Destroyer after all. You can’t be called the destroyer without destroying something. Much like how you can’t be called Umarak The Hunter without hunting anything.
Also, notice how there is a volcano in the background of UtD’s front box art thats erupting a strange liquid (or gas) thats the same color as UtD’s torso? There is also a ton of cracked and destroyed ground on all the beasts box art (including UtD).
If Umarak does blow up/“destroy” Okoto that would be cool to see tbh