Conspiracy theorists always have an explanation to support their conspiracy.
The fact is, you can make excuses all you want for Romo, but the team self-destructred in 3-4 consecutive Decembers (not all Romo years) and the celebrated - and celebrity - quarterback is going to take some heat for that. Especially when he made some very bad decisions in some of those games. It goes with the territory, and it's nonsense to suggest that only applies to Dallas QB's.
Another thing is that despite whatever legitimacy the excuses for Romo may have, perception is at least as big a factor as reality. A celebrity QB with celebrity girlfriends is going to have a target on his back, and the only way to avoid media fallout from that is to win it all. That was the key with the Cabo thing, and th difference between Romo and Brady. Brady was winning Super bowls while he was dating models.
The reality also is that Romo was elevated to star status, and actually celebrity status, way too soon. Before he had proven anything. When that kind of status isn't built on a solid foundation, it's bound to take a fall.
As for what sells, sure the Cowboys sell. But it's not just the negative. If we were perennial Super Bowl contenders Romo would get the same kind of lofty treatment Brady gets, but because we always fall short, he takes the hit. It goes with the territory of being with a high profile team. The glory and the failure are magnified.