Because I'm being reasonable about it?
I look at it this way, if such a video existed, owner of said video (other than AOC obviously) would have seen her skyrocket to fame and know they could make a serious truckload of cash on said video. Now, the DNC could have paid to keep it out of the public eye, but remember, she was NOT their favorite when she knocked off Crowley for his seat. Do you honestly think the national level party would have buried a video when she was in her primary battle with him? The DNC Caucus Chair? They'd let it get out just to improve his chances of winning.
Now, that being out of the way, we come back to money from a third party two years ago that would have paid out the wazoo for it. If anyone approached the adult entertainment industry with such a thing, they would have bought it and played it. And the moment it hit the internet, the genie would have been out of the bottle.
So, this whole "they'd pressure the website to not play it" doesn't go because this adult websites aren't going to ask for her permission before posting it. They weren't under any threat two years ago from financial companies to pull such things.
Again, if it existed, we would have seen or heard about it by now.