https://www.coh2.org/news/52176/esl-go4coh2-statistics-part-iii-commanders
Mobile defense is the most popular doctrine of the entire game during ESL. It was picked 92 times with a 47% winrate, compared to the 2nd place , Scavenger doctrine at 62 times with a 44% winrate.
if mobile is not "good", it's the best out of selection of "bad" doctrines.
And why is it picked a lot?
Because Puma provides a braindead counter to light vehicles. If you're dying to halftracks and stuarts or t70's you can call it in and it will give you a second wind in a game you would have otherwise lost.
You know what you can have at the same time as the Puma (6 cp ~12 minutes) if you have even map control and tech up? A stug.
The kind of situation where it works is like the game I linked, where Ostheer got his ass kicked and it's his only option to stay in the game, and even then it only works against an opponent who makes serious mistakes and isn't prepared for it.