I think Kimbo is easy to understand. A 240lb super swole black guy with a big beard, bald top of head, cool name, cool voice, turns up to bareknuckle fights in a hummer, was one of the first to have his fights go viral on youtube. He was even "Street Certified"
He's like the perfect internet sensation. I can't think of a single thing (other than legitimate fighting skill) that would have made him better received.
I think he made the right move going into MMA first as well tbh, he just happened to time it well enough that some people with more money than sense needed a 'name' to launch their organisation with. He made way more money as the face of Elite XC fighting cherry picked opponents than he would have in boxing.