You are very misinformed. The officer behaved properly and instructed the other officers to pursue the men who threatened him. Later in video same officers bring back one of those men in handcuffs. No one is charged because PC has taken over and the DA will not pursue charges.
The primary issue was the girl who was tackled.
Why was she tackled?
If she was doing something illegal, she would have been arrested.
Apparently, none of the 12 officers on the scene thought she should have been arrested.
The Chief and the city made to call to terminate the officer. Most likely from the accounts of the other 11 officers and the video.