A few reasons:
Dallas is notorious for choking. See the last 10 years of post season, inability to win with the dream team, Homo’s inability to hold a snap, etc.
Wade sucks.
JJ overmanages the team
Garett runs the ball down the teams throat to the goalline and then lets turnover prone Homo throw incomplete passes
RBs made of glass
A #1 WR Williams with #3 stats
I can go on.