Most people are pointing to the dunk as starting this.
But I think the coaches are pissed at Connor because they think he threw an elbow.
Watch the very end replay again, the defender swipes a few times, including what should have been a foul. Connor covers the ball and does a quick, short swing of his arms. The tv angle shows he didn’t make contact. But the coaches had their view blocked and could easily interpret it as having been an elbow to the ribs of their guy. That would explain why they were yelling at him before the handshake line.
He didn’t make the dunk, he just threw the pass up court to get away from a full court defense collapsing on him. So why would they have been mad at him about that? An elbow that they assumed occurred would explain the anger.
If refs aren’t going to control the full 40 minutes of the game, then they better be accountable for what happens in the aftermath. There should be a reprimand for lack of control of game for the refs and a reprimand to the assistant that instigated this blowup.