Foot stomps are a fantastic way to score points and win a decision in MMA.
When judging fights, I count strikes. Its very hard to judge striking in MMA, everything happens very quickly and it is very hard to judge the effectiveness of a strike without seeing physical damage on the figher. Often judges will judge a right cross higher than a jab. Or a head kick higher than a low kick. But that is also subjective as a low kick or a jab can do a lot of damage in a fight.
Something they teach you when you learn to be a judge is that blocked strikes are not counted. This is also subjective because strikes that are blocked can still do damage and be effective. But as a general rule judges will not count blocked strikes.
Foot stomps are a fantastic way to score points against your opponent where they can not score against you. They are very hard to block, the best you can do is avoid them. Using your arms to control your opponents upper body means its hard for them to throw strikes back. When you have your opponent up against the fence and you are landing strikes that counts as effective grappling so you are winning that criteria of the scoring system.
Check out Usman using them here:
https://www.reddit.com/r/MMA/comments/hvr88h/ufc_251_all_of_usmans_foot_stomps_in_1_minute/
and here: