Those companies don't own your backups and can't stop you from moving your instance somewhere else. And if you don't have a backup then it doesn't matter if you are running your instance in a datacenter you built yourself because you can inadvertently wipe the contents with a mere click

Anyone concerned with that threat model can host their own instance on whatever hardware they want.
They could have the middleware load balanced over aws/azure/gcp/hetzner/at-home and have load-balanced replicated postgres also running on those hosts.
They could use CDN & threat protection from those cloud providers as well as cloudflare. And really distribute the threat of that situation.
But nobody wants to fork out $$$ every month before they are even scaling to thousands of users, never mind the added complications of middleware from one provider trying to interact with a load balancer on another provider which is forwarding to postgres on a different provider, let alone geographic latencies.
Then trying to manage that, never mind the headache of an update.

But, if that is someones threat model, then they CAN work around it.

Companies owning the actual servers and infrastructure is at the level of enormous scaling (like twitter) or high risk (like banking, even then chances are they are running hardened systems that would be secure on anything).
Most companies will pass that responsibility off to a single provider, and rely on that providers skills/services for uptime

A regular court order won't be granted unless there's very good reason.

And it won't be issued to cloudflare to "delete everything that uses ActivityPub", because that's insane. And would require a bunch of manual engineering work.

And being distributed through cloudflare tells you nothing about where the files are stored. Because they're a CDN.

OVH server owners learned their lesson not to keep their backups on the same hosting provider after the fire a few years ago. The only problem I had was actually getting OVH to give me a new server to restore my off-site backup to!

If you have backups independently of your hosting provider AND your domain isn't hosted with them. The worst they can do is take you down for the time it takes to get a new server elsewhere, restore your data and point your DNS (or CDN endpoint) to your new home.

If you're running a fediverse server and at the bare minimum don't have your database backed up somewhere, then the fault of any takedown is as much your fault as your hosting provider.

Mine is first backed up nightly to a server on another hosting provider, and that in turn is backed up to encrypted cloud backup.

And it will take me all of 60 seconds to turn off cloudflare on my instance I I ever have to and 5 min for TTL on the DNS to expire, bit in saying that I have moved from a small indipendent VPS to a much larger provider for cost saving (Mostly for storage, but also double the core count).