I still don't get how diamondhead defeated vilgax in AF while chromastone and humungousaur couldn't

I love diamondhead, one of my favorites and I lean more towards the classic 10 than the alien force 10 aliens, but I still don't get how ben won with him while he lost with humungousaur and chromastone.

Aside from that, that moment was epic, seeing diamondhead return, beat vilgax in an epic way was cool, not to mention I loved every time we got a classic alien in AF and UAF(still wish ripjaws appeared in that one episode where they go to his planet)