Characters like him shouldn't have a fb and it still be ok...
The main role of Kaido in these story is strength and power.
He's legit hardcore villain that pretty much have no or doesn't need justification on how he's gone bad.....
He's just there in the story to be bad the bad guy........he got the strength and power inexchange for the lack of so-called character at least.
We just want a villain to have a deep emotional backstory on why they become this and that.

You see, just like how the Joker movie was adorned by many ppl.....
I don't personally care about it.
Character like BB are already interesting to me even without backstory, they do not need justification, they're just evil and enjoy chaos, that's just about it.
And i hope Oda doesn't do any emotional well justified backstory for him.....