Why is Kefka considered one of the best villains in the franchise?

I just finished FFVI and it was a great experience. It has entered my top 5 favorite FF ever made, even top 3 probably. I really think THIS is the FF that deserves a full remake. But there is something that has caught my attention.

I've been hearing for decades that Kefka is one of the best villains in the series, even the best. When someone says that the best villain is, for example, Sephiroth, I've always seen someone say "you say that because you don't know Kefka".

II don't get it. The character design is great, and I like that he is not the perfect edgy villain, I'm glad he makes mistakes and has some sense of humor, but the rest seems to me a very shallow character, he has no backstory, he is a psychopath unleashed because the experiment to grant him magical powers had severe consequences in his mind, ok, basically he is bad just because he is, nothing else, there is no character evolution, no interesting contradictions in his way of acting nor a solid logic behind his ideas, he just repeats pseudo nihilistic phrases. There is not even a deepening of his madness, he is just the typical "evil crazy clown" and nothing else.

Honestly, Sephirot or Kuja seem to me deeper and more solid villains. Even Ultimecia or Yu Yevon, who barely have any direct presence in the games have more logical motivations.

Am I missing something?