People initially didn't like him because he was a bit cringe in his interviews early on in his career and people tend to want a reason to hate dominant champions that are really confident.
I think people also mistook his confidence for cockiness.
His actions were always classy, he never ducked a fight, never made excuses, and took his KO loss with good humor.
On top of that, he took fights on short notice while not being 100% (shot knees) against TOP TIER competition in a HIGHER WEIGHT CLASS. I've come to really appreciate him as a really good champion and fighter that is durable, hits hard and dominant wrestler.