I would say Dallas won it but both teams tried pretty hard to let this one go.
Both throwing the INTs that went for TDs. Each team with an additional turnover. Dropped passes by both teams. Poor pass defense by both teams.
The Rams had more mistakes and the Cowboys were able to make a play when they really needed to.
I think the Rams coaching staff had a couple of questionable decisions and they are ultimately to blame. On the possession just before half when the Rams had 3rd and 1 at the Dallas 44 with 0:42 remaining, they came out in the shotgun with an empty backfield. Awful call from the start and they fumbled the snap. IMO, this is an obvious power running situation. You either get the first down or at worst you force the opponent to use a timeout. Dallas got the ball and scored a FG to end the half.
The other is obviously passing on the FG. An 11 play drive that takes almost 6:00 and gets inside the Redzone should never end without something on the board.
I think the Rams gave Dallas plenty of opportunities to get back into the game and Dallas took them. Don't give away easy points to your opposition and don't take points away from yourself simply because of coaching.
I think both teams played well enough in some aspects to win the game, and poorly enough in other aspects to lose the game. I think Dallas was just on the better end of the coaching spectrum on this day while the Rams were on the poorer end.