I've been thinking since this happened that you can draw a straight line between throwing Sergio out of the club and this incident. When Gronk gets enraged on the field, he wants to physically dominate someone. He expresses his frustration physically. In the case with Sergio it was over trash talk, there wasn't great video of the most egregious part of the play (minus the above still which made the rounds), and most importantly, Sergio didn't get hurt and there wasn't a head-injury element to the incident, although there easily could have been. And then there was the great quote after the game that cast the incident in a funny light rather than a predatory/malicious one. He was fined for the play, but everyone had a laugh.
Gronk saw red again on Sunday, and got overly physical in a stupid, frustrated way. He just lost control and wanted to hit someone, maybe even hurt someone. This time, the focus of his rage was already on the ground, and so the awkward body slam was probably the first thing he thought of.
Stupider result, same process.