They cannot take action based on vibes, they need concrete evidence. With LoTT or KF it's pretty straight-forward because of media reporting on the threats that follow in their wake.
Singal has subverted the journalistic establishment (eg his cabal's group chats:
https://www.jezebel.com/private-messages-reveal-the-cis-journalist-groupthink-b-1827041764)
Turns out when you're literally in group chats with other journalists, and use your influence to have your journalist buddies defend your "freedom of speech" and "integrity of independent reporting", it's harder to get reporting out about how you harass people. LoTT has fewer such defenders.
Networked harassment is hard enough to call out when it's individual actors or pseudonymous forums. When someone uses the cloak of journalism to engage in it, the standard of proof rises substantially and the number of people who will look the other way for a "fellow journalist" increases.
This makes the accusations of a "trans group chat cabal" even more hilarious, because they absolutely are telling on themselves when they make the accusation that trans people control the media.
Mate, if we controlled the media, Guardian (UK) or the New York Times wouldn't run hit pieces every week