Andre Drummond is great at corralling the ball when it's near the rim. His lofty rebound numbers prove that. He's also capable of using those skills on offense to set up big dunks.
Reggie Jackson got credit for an assist on that play. It's possible he was intentionally throwing that up to Drummond after his defender rotated. It's also possible that he just took a shot so bad it looked like a pass. Either way Drummond took care of the rest.
Mike Prada broke down the effectiveness of the Drummond-Jackson pick-and-roll and it really is a no-win situation for defenses.
Much of that is due to the threat Drummond presents. He is so dangerous as a roll man and offensive rebounder that opponents don't want to leave him alone. This creates openings for others, but it especially creates openings for Jackson to score. When Jackson comes off a Drummond screen, he can slowly advance to the hoop without the defending big man really being there to stop him.
The Cavs left Drummond and found out the hard way what happens when you do that.