Throwing the ball allows you an extra attempt to score. It increases the likelihood you win that game. Throwing a pick at the goal line is an incredibly unlikely result.

With unlimited time on the clock you run the ball, but with only one timeout and limited time left you have to maximize your chances to get a score, and throwing the ball does that. It was the right call. Bad execution, but the correct decision.

It's 2nd and Goal with 26 seconds left. You run the ball

Result 1: Touchdown -> win the Superbowl

Result 2: Stuffed short -> Call timeout -> 3rd and Goal with 18 seconds left and no time outs. One real play left

It's 2nd and Goal with 26 seconds left. You throw the ball

Result 1: Touchdown -> win the Superbowl

Result 2: Incompletion -> clock stops -> 3rd and Goal with 21 seconds left and 1 time out. You can still run the ball twice.

The chances the Russ throws a bad ball that close to the endzone, and that the DB reads the play that quickly, and manages to come up with the INT are extremely small. 

I'll amend this by saying it's the statistically right call. I would not have called it.