Several are to blame on this play.
First of all, Looney and Dak should have realized the more easier lane to run through, due to the Rams alignment, was between Center and Left Guard. They both should have noticed that and changed the obvious destined run behind Right Guard Zack Martin to Left Guard Connor Williams.
Secondly, the whole Oline does not fire out at all! Frustrating to watch. You need 1 yard to get the 1st down at the Rams 30 yard line early in the 4th with the game on the line. If you get that 1 yard and convert the 1st down, you get to keep the drive alive and potentially score the tying TD at that point. Momentum would have gone to the Cowboys. Instead, the whole Oline just stands up and allows itself to get pushed back. Inexcusable! This is why I'm constantly getting after this Oline consisting of a bunch of 1st rounders because it is crystal clear they are not being coached and trained correctly. Just watch the tape. They all stand up haphazardly and allow themselves to get pushed back! Had they been trained to FIRE OUT AT THE LINE OF SCRIMMAGE AND GAIN LEVERAGE MOMENTUM, the law of physics says they would most likely win the battle of leverages and be able to push the Rams Dline back, thus creating holes for Zeke to run through. It all starts with the Oline and how they are being coached!!!
Lastly, Zeke has to realize the Rams are clogging up any gaps right of Center Joe Looney. In other words, the Rams are betting the play is set to run behind Right Guard Zack Martin, which it was, and are tempting the Cowboys to run the ball elsewhere. Since it's obvious that Zeke was not going to deviate from the called running play set behind Zack Martin, he should have noticed the Rams aligning themselves to stuff that gap, thus either decide before you get the handoff to either follow the designed play and leap over the pile in order to gain the needed 1 yard or get the handoff and run towards the obvious open gap between Center Joe Looney and Left Guard Connor Williams...and hit it hard! Instead, Zeke gets the ball while keeping his head down and haphazardly runs right into the pile between Joe Looney and Zack Martin.
What a terrible attempt by everyone. No one fired out or came out with aggression. They all played at half speed as if they were nervous and didn't want to get that 1st down. The Rams had much better effort off of the line of scrimmage.