Many of the protests were violent. Federal buildings were attacked and Federal personnel have been harassed and assaulted. The local authorities have not been able to restore law and order. There were riots long before Trump decided to act. Trump should have sent troops in long ago, but at least he is finally sending in Federal agents now to arrest those who are committing violent crimes and fomenting riots.
https://www.oregonlive.com/portland/2020/07/hundreds-of-protesters-gather-outside-police-union-in-north-portland.html