He was resisting arrest and repeatedly disobeyed orders. He then proceeds to go to his car.
They have no know of knowing whether he's "running away" or going to get a weapon. It's easy for you to armchair quarterback after the fact, but in the moment on the ground, they have no idea what he's trying to do. There have been multiple instances of people going to their cars to get weapons.
Cops don't have to let you go if you are resisting arrest, and especially not if you reach into a car/compartment/pocket. What fantasy world are you living in?
I've found an example of how you would like cops to act, I think this is a fair assessment, yes?