Case law is important in the UK because laws are vaguely written and thier specifics are established in court.
By going after entities that can't comply and don't have a big legal budget like 4chan, they can go through the motions and establish that ISP level blocks against non complying companies are okay.
They can then hit progressively more difficult targets until they get to X and tiktok.
https://en.wikipedia.org/wiki/UK%E2%80%93US_extradition_trea...