The failures on January 6 are particularly stunning. Anyone who has been to an anti-war or other protest at the Capitol can tell how heavily guarded the Capitol is. Anti-war protesters are arrested for merely being on the Capitol steps. There is no scenario in which people at an Act Now to Stop War and End Racism (ANSWER) march would have been allowed to breach the Capitol and send members of Congress into hiding.
On top of that, much of the planning for January 6 was done in plain sight. Anyone vaguely paying attention to the news had some inkling of what was afoot. It makes the police response all the more perplexing.
I feel like this would benefit from more detail. The argument seems to be that the FBI should have prevented the Jan 6 insurrectionists from gaining access to the capitol building, given its extensive surveillance powers. That their failure to do this, their failure to prevent 9/11, and their attention towards left wing protestors is evidence that the organization is misusing its powers and not doing anything useful.
Did the FBI have investigations into the Jan 6 protestors going before the event? My understanding has been that they got in because there were just so many people refusing to follow instructions, not enough guards to begin to control a crowd of that size, and they didn't go as far as to start shooting them at first. Would they have shot left wing protestors doing the same thing before they got in the building? Would they have arrested them prior to the event on the basis of posts online talking about getting into the building? Or is maybe that just not how the FBI works? I don't really know. I agree with the article that there should be more investigation into what they do and more oversight, and maybe not allowing the executive to have as much ability to wield it as a political weapon, and changing the law so they aren't exercising so much unaccountable power over American citizens.