It sounds simplex but my answer to the OP is DON KING.
In the 80’s and 90’s he turned boxing into a circus and was one of the reasons so many “associations” and “commissions” continued from the 70’s. This is why there are 50 different champions. Boxing now days has no more honor or respect than “professional” wrestling.
I sorta agree with this. The thing is, boxing has always been corrupt. Always. And people have always known that it was corrupt. It’s actually probably less corrupt now than it was at its peak in the mid-20th century.
But that corruption was always in the back rooms, in the shadows. Don King was a celebrity, larger than life, and he really shoved our faces in the corruption. His open, blatant manipulation and corruption was just too much for many sports fans to deal with.
Sadly, the corrupt people running it back then did a better job than the corrupt people running it now.