My opinion is that this is mostly pre-election posturing by the Democrats on all levels, who get their marching orders and script from the DNC. Barr is stamping down on Antifa cells, and their liberal enablers/handlers in the government and media are attempting to utilize this as a "DRUMPF ist Diktator!!!" line to confirm their narratives that Trump is about to send everyone to extermination camps.
They want more protests, and also more clampdowns, in the hopes for a Kent State situation- note how they were almost gleeful at the Antifa member who got teargassed in the noggin.
As for why the DOJ chose now as the time to clamp down on Antifa, it may very much be part of a continuing operation- in that data collected from earlier riots has been collaborated, and the Feds are now snatching up key Antifa operatives and sentencing them with the evidence to lock them away permanently, as opposed to Liberal mayors and DA ordering catch-and-releases.
I do expect that Antifa/the Democrats had plans for more unrest in the late summer/early fall during the election, and disabling Antifa before then is a priority.
As for the Democrat response, I fully expect them to further the charm offense on behalf of Antifa ("peaceful protestor" narrative, hiding the violence), and to try to get an injunction via some activist judge, as what sort of police department is going to accept being sent out on behalf of people who hate them?
better