I'm no Xbot fan or nothing, but I hope no one at Microsoft is holding the yet to be launched Xbox One against Mattrick at this point. It's not like Microsoft has had any successful consumer electronics launches other than the Xbox and Xbox 360 in the past. Any one remember the Zune Media Player? Microsoft Kin smartphone? The Surface, anyone?
And honestly, does anyone expect the Xbox One to be a flop? It may under perform, but it will sell millions of units and have substantial market share.
While Mattrick isn't solely responsible for the Xbox One's PR disaster, as the head of the Entertainment and Devices division at MS he was responsible for the overall strategy and they have made numerous strategic errors under his leadership.
1) The DRM debacle is the most obvious. The fact that Mattrick didn't anticipate the scale of the backlash and have a PR strategy in place to deal with it was utter incompetence. As you said, MS were completely unprepared at the reveal event, and the fact that execs couldn't keep their story straight on how the DRM would work gave the impression that MS were trying to obfuscate the issue. Mattrick also had his own personal PR blunders, particularly the golden "buy a 360" soundbite.
2) Sony beat them on price. After being burned on the $599 fiasco for PS3, it should have been obvious to MS that Sony were going to target a price in the $300-400 range and MS should have aimed for the same price-point. The really damning thing about that is it was a self-inflicted wound, if they hadn't insisted on bundling the Kinect with the console then they would have matched Sony on price. That looks to have been a big mistake.
3) There's evidence that MS are several months behind schedule and are rushing to meet the launch deadline. There's rumours that Sony will beat MS to begin mass production and that MS are having yield issues with their APU, rumours which appear to be substantiated by the fact that preorder allocations for the PS4 are 2 or 3 times higher than the Xbox One. It will simply be easier to find a PS4 for sale this Christmas, which means Sony should have a larger install base to build off of. That could put MS at a massive disadvantage long-term.
4) Under Mattrick's leadership, Xbox's standing among core gamers has declined. Exclusives have dried up, MS focused their attention on Kinect and casual gamers, while their E3 presentations in recent years have been cringe-inducing. The casual gamer strategy was successful for them in the short term, but core gamers, the ones that are going to be the early adopters for these new consoles, have grown weary of MS. With the PS3, Sony has shown a dedication to releasing quality and diverse exclusives over the life of a console, and PS+ appears to offer much better value than XBL Gold. Sony has the better reputation with core gamers over the last few years.
MS got outmanoeuvred by Sony this time, but it was mostly because of their own screw-ups and not because Sony had an amazing strategy. Mattrick has to take much of the blame for that even if he's not wholly responsible.