I believe that play went as designed, Sam read it perfectly, and played it almost perfectly. You want to take zero risk there, and if the receiver isn't WIDE open, you toss it in the dirt, running a few seconds off, and stopping the clock. I say almost perfectly because it would have been nice if Sam held the ball for another second or two before throwing it in the dirt.
If the receiver is WIDE open, you take the 5 yard gain, and then get to the line to spike the ball. That should leave you with around 8 seconds on the clock. I think Sam read that JSN was well covered, and the interception risk was too high. It would have taken a perfect block from Kupp to take two of the three defenders out of the play. I think Sam saw the defensive alignment before the snap, and chose the ground.
Given the way the refs were calling the game, Sam needed to make it look like a very legit attempt to connect with a receiver. No leeway would be afforded just because "there was a receiver in the vicinity." They would have happily tossed an intentional grounding flag if he merely threw it in the vicinity.
There would have been no time to get the field goal unit out, if the clock had been running after that play, plus it would have added additional, unnecessary pressure on Stoll, Dickson, Myers, and the blockers. It takes 15-25 seconds to swap to the kicking unit, which would give them 7 seconds to kick, if everything went perfect. You know the ref would have happily stood over the ball for several seconds, while the game clock ticked to zero, to "give the Colts sufficient time to match the Seahawks substitutions."
The absolute worst things that could have happened, in order of badness, interception, sack, receiver stopped short of first down.
