Not all just watched. The older guy in the foreground seems to be trying to tell them to stop. But I think it is the expected reaction. Many too stunned at what is suddenly going on to be able to react. Some not taking notice of the commotion until they finish what they're doing. The rest wondering if they should get involved in someone else's dispute, and not wanting to be a victim themselves are inclined not to stick their nose in. I think it is the few that act, wade in, then think afterwards. Probably always will be. That's why a uniform helps, but there are few coppers on the beat these days, you are unlikely to find one nearby. Still the CCTV stopped it immediately, so that's ok; oh hang on a moment ...