Who or what exactly might be conducting the current DDOS attack against PieFed.Social?

EDIT: TBC, here's the current message seen when refreshing a PF stream:

"Piefed.social is having a denial of service attack. They are being kept at bay for now but could return with a more effective method. Download your community subscriptions so if you need to move to another server it’ll be painless - with a few clicks you’ll be seeing all the same content as before. See list of alternate servers at here or here."

Possible causes?

• Fellow instance that got PO'd somehow? (seems like a major stretch)
• Just random hackers havin' fun?
• Reddit or similar, targeting one of the top growing instance softwares in ActivityPub / FV? EDIT2 : the timing certainly seems to fit for the recent influx of users coming from Reddit. (see comments)
• Some right-wing entity, not happy about the general rational / left bias to the instance?
• Other..?

In any case, much thanks to our instance runner and dev for fending off the first wave(!) Hope everything is backed up and possible to be restored if the worst happens.

(seriously, what a shitty way to be repaid for doing a great, ongoing job for the community and FOSS)