Same here, but I understand why he did it.
I think this first game came down to which team wanted it more and the Rams play in the toughest division in the NFL with few L's to give up and were opening the new 5B stadium. The state of the East and PHL's problems, seen as the only challenger, gave the players a false sense of security. This game was far more important to the Rams than the Cowboys.
According to the reports, McVay spent the off season trying to toughen his OL and run game up and starting off like that was just what the doctor ordered. They were 9-7, playing an 8-8 and opening a new stadium on the Game of the Week. The Cowboys, undeservedly so, get a lot of Game of the Week's.
I don't have a problem losing that game because I like finding out what a coaching staff and team is made of early on. They weren't going 16-0 so what's the big deal?