I have not read other replies, and this was probably stated numerous times, but this is what happens when the police fail to do their jobs.
Only one group came with plans of violence and anarchy. The other group defended itself from attack because the police failed to do their jobs and preserve order.
If ANTIFA’s meet no necessary resistance, they will break and burn things seeking affirmation; attention; notice.
The cops have a much easier job: everybody goes: The bad guys are not mixed up with the them. Pressure to take time to analyze what is the right thing to do is no issue at all.