Ok, just watched this fight. My take on it:
1- It wasn't that close. I gave 7 rounds to Floyd. And honestly, Floyd is a much better boxer than Castillo, so even if it was that close, i'd still be ok with Floyd winning.
2- People get overly excited with the possibility of Floyd losing. Any match where the opponent puts up a fight people tend to claim Floyd lost.
3- People are easily impressed by quantity over quality.
4- The commentators were brutally biased towards Castillo, often ignoring the clean shots Floyd was landing to rave about everything Castillo supposedly landed.
5- Crowd would cheer everytime Castillo came close to land anything. You just can't get a more biased environment than this.
6- Castillo spent the night hitting air and arms. Did a decent job at hitting the side of the body, but barely landed any clean head punches. A lot of work, a lot of quantity, but not that much quality. That's why Floyd won.
7- 80% of the time a clean head shot was landed, it was landed by Floyd. And i mean a shot where you can clearly see the head snapping back from the power and clean connection. Castillo barely connected with Floyd's head. Floyd was just slipping those punches. Very little was landing clean, but people counted them as clean shots, even though they weren't.
8- Floyd fights in a way that leads people to believe he is getting hit when he is not. Same in the Conor fight. People thought Conor did very well, and landed this and that, then you watch the fight from the crowd angle and he wasn't landing shit. So when an opponent throws a lot, it gives the illusion of connecting, when it didn't. That's why you rarely see Floyd's head snapping back from the power. Those punches aren't connecting at all.