Not only did we not sneak, there was a clear gap on Steen's right side. Tannehill could have easily taken the snap and gained the 1st down.
It's a good enough play for Tom Brady -- who doesn't have half Ryan's athleticism.
It's really hard to stop a QB for no gain unless the defense times it absolutely perfectly, which is difficult to do. While no play is foolproof, your chances of converting 1/2 a yard when the defense stacks the box in short yardage is much greater with a quick hitting QB sneak than it is with a longer developing conventional run play that allows time for the defense to penetrate.
It's not rocket science, but most teams seem to make it out that way. I guess that's why teams like the Patriots win consistently -- because they use high percentage plays, the QB sneak being among them.