People are actually dumber than I thought.
So Kizaru dancing a dance that pre-dates Luffy, because he "worships" a God that exists way before Luffy, is him twerking for Luffy.
He knew who Luffy was, and he gave Zero fucks about it, unwarranted hate.
Mind you aswell that he might have joined for the sake of it, and not because he believes in it, he saw them dancing and danced.