Any de-federated instance doesn’t have the money or resources to start DDOS attacks.
It's shockingly cheap and easy to DDOS people, especially if you know something that makes them exceptionally vulnerable as is mentioned in the post above. Small-time wanna-be hackers can put their allowance savings into getting a DDOS running just to be spiteful little shits.
Sure, could it be a corporate attack? Of course it could be. But could it also be some spiteful little fanboy who just wants to piss on people who want to do their own thing? Of course it could be that as well. And dismissing that as impossible is simply wrong.
Huh... For troubleshooting, would you be able to boot into something other than Windows and see if the problem persists?