This may explain why the DEA, but not why protestors, as opposed to looters
Cop brain is very simple: You wither listen to the cop or you are a criminal. There are no shades of grey, and the US police have demonstrated this across the country this weekend.
https://old.reddit.com/r/PublicFreakout/comments/gvmhh6/fbi_...
On one side, you have the generally disorganized public which naturally includes the opportunistic, the provocative, the desperate. On the other, you have the police and the military, nominally organized with a largely uniform mission and code of conduct.
Bad behavior by the government is less excusable and also more threatening.
I also think there may be some suspicions that some violent instigators might be acting at the urging of a foreign government - which is the domain of the FBI.
I think it's reasonable to help them in that effort - while also condemning the police for their role.
The death of ONE MAN, George Floyd, caused mass outrage. If a foreign directed agent is able to instigate a similar tragedy, I think that's very very important to nail down.
"...to enforce federal criminal laws in the wake of protests..."
So not protestors, but criminals taking advantage of protests.