What even is Kwanzaa and who even celebrates it?

So like all the cartoons I watched as a kid had it, i celebrated it at school, but I have not met a single person that ever actually celebrated it.

Like my class was fairly diverse so I would ask the black kids and they would say "no we're Christian" or "no, we're Muslim" which was weird because when I was a kid I thought it was the black Christmas. So when I got a little older I discovered who the creator was, he is a black nationalist and an atheist who believed that Christianity controls the black man, ok understandable. Also he tortured women and was a fed.

But that gave me even more questions? If it's not for Black Christians (the majority of the black population) and is apparently meant for black atheists but don't most atheists celebrate Christmas anyways?