Different workplaces have many similarities. The Social Sexual Hierarchy remains the same. Alpha's often get promoted, because Alpha. Here I advise readers to read Political Ponerology, on this very topic.
So, your average cop-shop is a hierarchy. Your beat cop likely can't do shit without all sorts of career threats, so I do have some sympathy. In a previous place of employment, it was practically a police state: cameras in the office, spy-tools on the laptops, work routinely audited, strict hierarchy with a democratic veneer. I've no idea how to run a business; presumably this is just how it works. In law enforcement, the beat cop makes no decisions, and is unlikely to step out of line: chain-of-command is very real.
Who is ordering cops to stand-down in the face of rioters? Those at the top of course. The Alpha dog with ambitions to be commissioner knows that he'll be fired if he disobeys. Likely, he is so indoctrinated the thought scarcely occurs to him. The beat cop, the Delta male, probably knows better, and is disturbed by the looting and rioting, but he's a worker-bee looking at retirement, what to do?
And so it is we see how corrupt law enforcement is in the US. It's top-down corruption that has build over decades. It's Governor, Mayor, Commissioner, State AG, all conniving and plotting with no care for the people of their state. A civil war requires two sides fighting, and currently we only have one, looting and rioting. Kneeling in front of cops for a photo makes nobody Malcolm X. And stealing a flat screen simply makes one a thief in the night, as Smaug might say. The riots are no longer about race, if they ever where. As they say in election year: it's the economy, stupid.