CM Punk's Biggest UFC Mistake Was Not Playing A Heel
While there were many, one stands out.
While even attempting to compete in the UFC could be considered a big mistake on the part of CM Punk, his defeat - while brutally decisive in nature - wasn't so bad that he suffered anything more than disappointment and a few cuts and bruises for his efforts.
The worst mistake CM Punk made during his brief UFC career, that according to Dana White has probably come to an end, is that he decided to embrace the role of the humble outsider who was just happy to be there. As a pro wrestling performer Punk had many strengths, but none more so than his ability to manipulate a crowd through the use of his promos. He's a massively charismatic talent who belongs on any list of greatest mic workers in sports entertainment history.
CM Punk was at home in the role of the heel, with the freedom to unleash his naturally abrasive personality and get paid to piss people off. It was one of his best qualities as a worker and that skill went entirely untapped during the UFC experiment.
Throughout this entire ordeal Punk was cordial with the media and the fans, something that's uncharacteristic for him. But with to so many MMA followers and many of the fighters themselves outright stating their resentment for Phil Brooks and the position he was given based on nothing more than his stardom, the situation was ripe for Punk to revert back to his wrestling roots and go full heel.
For as many amazing competitors as there are on the UFC roster, there's less than a handful who are draws based on their personality and charisma. Conor McGregor has talked himself into becoming the top draw in the sport, and Chael Sonnen became a superstar by being an above-average fighter with elite level mic skills. It's a quality that's sorely lacking in the sport and there was an opportunity for Punk to step right in and set the MMA world on fire with his mouth.
The fight was going to play out the same way regardless of whether or not Brooks played the nice guy "aww shucks, I'm just here to give it my best" role or went full *sshole and told the entire roster to suck it. At least if he had utilized his natural talents - which don't include striking, grappling or any aspect of mixed martial arts - he would have made a much bigger impact, drawn more money and justified the UFC investment in him, which might have extended his career with the company.