You move in to arrest. If the crowd moves in, you spray them to protect your life. You don’t spray people sitting on the sidewalk in anticipation of something maybe happening.
Have you been in situations where you are outnumbered by a hostile group? I have.
There is a way to remain in control of the situation. You just have to give each member of the group total certainty that you will inflict unacceptable levels of damage to the first person who makes a move. As a group, they may be confident they can take you. As individuals, nobody will want to be first.
By inflicting a minor level of pain on the group, the police reduced the probability that the crowd would do something that would NEED to be responded to with deadly force. They saved those idiots from potentially dying.
Here's something you really need to understand about police mindset. The cop intends to go home uninjured at the end of the shift, by whatever means necessary. THAT is his top priority. If the only way to accomplish that is to have a large pile of bullet-ridden bodies for other to deal with, then there WILL be a large pile of bullet-ridden bodies, despite anything that the political authorities have to say about it afterwards.