There's quite a bit more to that article. This does not appear to have been a "prank." A fraud, perhaps, but not a prank. The account posting this has a lengthy history of appearing to be "antifa" with particularly far left ideas, the very kinds of ideas maligned most by the right. And is oddly helpful to Trump, attacking Biden for being a "rapist," for example.
Notably, the investigation could not identity the person in question, as the name given to the media is fake.
The most likely scenario is that whoever posted this is in fact with the far right. It's of a piece with the Boogaloo Boys posing as antifa online, pretending to organize antifa for the BLM protests.
More than likely, whoever put out this message hoped that actual leftists would show up to burn flags and this would make the left look bad. It didn't happen, so the chuds who showed up look like they got pranked, but in fact the entire thing was all in the family.