I haven't watched. But I know why I lose when I do.
The biggest reason I lose is because I am unfamiliar with what my opponent's option are in every given situation. I was more familiar with available options in MK9 than I was in most other games, and because of that I was better at MK9 than the other fighters during that time. Lack of familiarity with options as well as the corresponding frame data and what to counter with - number 1 reason.
Second reason is trying to play too many fighters and bringing tendencies from one developer to another one when those tendencies don't translate. MK9 fundamentals are not Street Fighter Fundamentals.
Execution would be third, but that's just muscle memory and really isn't a big part of the reason people lose, at least for me.
I can think of examples of this pretty easily. I didn't know that you couldnt anti air roll bojutsu kung jin's jump in. That made me lose in a tournament. I didn't know that a quick DP was a clean punish for Makoto's dash move (whatever it's called) and my opponent just spammed it on me without getting punished for it. Plenty of other examples
tl;dr: Lack of significant matchup knowledge and flaws in tendencies learned from other games. Does it take him 53 minutes to say that?