We had a bunch of Japanese teenagers run scripts on their computers and half the Fediverse was full of spam. If someone really cared about spamming, this shit wouldn’t stop as quickly.
The upside of that attack is that instance Admins had to raise their game and now most of the big instances are running anti-spam bots and sharing intelligence. Next time we'll be able to move quickly and shut it all down, where this time we were rather scrambling to catch up. Then the spammers will evolve their attack and we'll raise our game again.