Great way to to maintain order

Major difference between 'protestor' and 'rioter'.

Protests can turn into riots, and people can get arrested just trying to escape.

Don't forget, the law runs on an 'innocent until prove guilty basis', so even if you do get caught up in a riot, if you don't smash stuff, and do t participate, you won't be tried as an agressors, however, if for instance there's CCTV or bodycam footage of you throwing bricks at windows, you should pay the fine

Of course.

bruh https://www.youtube.com/watch?v=ThlHyf7jWNQ

Okay, cops make an arrest (at the scene of the crime or shortly thereafter) and use video to identify suspect. Same as all crimes. This honestly just proves that proof is possible. I saw numerous faces who were both damaging AND not damaging. Not all criminals would be caught ( same as all crimes) but the OP said it was a division amongst all who were CAUGHT. Nothing new honestly.

The suggestion of the OP was not a cure for this situation, but a band aid at best. Arrest with proof would not be fool proof, but neither was the suggestion.
The criminals are still taking one fuck load of a gamble.

It just helps the state, or possibly individual companies (depending on where the fines go) recover a little easier

As said above - CCTVs, body cams, eye witnesses

From a crowd of potentially thousands? Do you remember when they fingered the wrong guy for the Boston Maraton bombing? Imagine that happening on a much larger scale.