They normally have to ask for dates, permits, are normally driven by groups that have been around for long, they have websites, they have a list of asks, etc etc.

Compare that with violent ones that see the opportunity coming with 3-4d heads-up (because peaceful protests are normally covered with a little advance - 3-4d - by mainstream press), create an Instagram/TikTok/Whatsapp/Snapchat group, spread it aggressively thanks to zero cost of social/IM, and their only objective is to smash everything in their path (and if they manage, steal some loot to resell).