This article here seems to capture what people are thinking about the Pacman-Mayweather fight. I don't think it was anyone's fault. I've boxed or coached boxing for neigh on 10+ years. I think what people did not understand who know next to nothing about boxing is that this match was never going to be a Rocky film WWF style brawl, despite whatever people thought it was going to be. That's not real boxing. That's thugs duking it out in the Thunderdome: "two men enter, one man leave." Rocky was the worst thing that ever happened to boxing because it ingrained in novice fans' mind that boxing is about going to for the killer head shot to knock the dude out. Very rarely do head shots ever make someone go to the mat. Head shots stun and you go after the gut. It's when you get punched square in the gut that you go down to the mat.
These were two extremely good professionals whose strengths were both in the defensive, not offensive, mode of boxing. There may be have been more brute force and knock out power had they fought 4 or 5 years ago, but both of these boxers are notorious for defense. No one does defense better than Mayweather. He's made a career of it. He adapted and basically took away Pacman's left by the 4th round. Being a southpaw, that was Pacman's bread and butter when going for the KO. Pacman didn't really seem to have a offensive plan B.
If you go back and watch, Pacman was very good at getting Mayweather into the corner, pretty much every round. Mayweather very rarely ever did that to Pacman the other way. This is why he thought he was up on points. Pacman was manuvering very well, but once he got Mayweather into the corner, Mayweather, being the defensive genius that he was, would always neutral the attack and squeeze out of the corner before Pacman could do any damage. That was a fatal flaw.
Now, true, Pacman has never been the same since we was KO'ed a few spaces back. He wasn't nearly as agressive as he was in his younger days. That played right into the hands of a defensively minded Mayweather. I think he is probably going to ride off into retirement in the next few years. But, I think what people don't understand is that Pacman was thinking long term if there is ever a rematch. His defensive game plan was looking towards the second game. Long term thinking is always going on in boxing. He was systematically testing every single defense that Mayweather had. Go back and watch, it's very interesting. What people think is him being passive and making a terrible fight was actually quite brilliantly setting up a rematch. He knows what he's up against now, and if there ever is a rematch, he's in a much stronger position going in. He's now seen everything Mayweather can throw defensively. Mayweather hasn't seen everything Pacman can throw offensively. This match was a longer term head game, and I think most people watching it didn't grasp that. Keep that in mind if there's ever a rematch.