BYU DOESN'T have the depth or talent that Missouri does. It's a matter of fact that they recruit better athletes than BYU does (on average). And it goes without saying that they have a very good, very talented, very experienced coaching staff that knew how to exploit BYU's personnel weaknesses.
Why would you EXPECT BYU (with all of our recruiting and other limitations and disadvantages) to beat Missouri? I can understand hoping to beat them, but, I don't see how anybody with a grain of objectivity could expect a BYU team that has been decimated by injuries and suspensions to stroll into SEC country and come out with an automatic W against a team as physically talented as Missouri. There are reasons that even mega-teams like Alabama don't come out of the SEC unscathed.
Missouri isn't particularly good this year (especially on offense), but they're still a much faster, more athletic team than BYU is. They're a team that is more than capable of winning one on one matchups against our cougars. BYU would have had to play a disciplined, mostly mistake free game to beat them. They didn't do that and they lost. That will be the case whenever BYU makes critical mistakes against teams with the kind of talent that Missouri has.