Blocking Cloudflare itself wouldn't make any sense as our country systems themselves would get hurt and I don't think Cloudflare will deny such order.
The money X Corp is paying them cannot be THAT great to justify losing all brazilian costumers and Cloudflare doesn't seem like a very ideology-driven company.
Lets remember that Twitter is not their only customer..
So if twitter has problem with some country justice it is their problem to solve, not a problem to be shared with every other Cloudflare customer..
Also, i doubt that they are making more money from Twitter then every other customer in Brazil added together..
The precedent is already set, this is nothing new..
cloudflare offers a lot of self-service tools, which can and do allow customers that cloudflare doesn't want to service to use it until someone finds out (my favorite example is that, briefly, the foreign ministry of Iran briefly managed to register and activate properties on the service)
registering while only directing brazilian clients to cloudflare would be difficult using the standard method (setting your domain's nameservers to the cloudflare servers), but cloudflare's CNAME setup option only requires a TXT record. it's possible x.com did that by just paying for a business plan and never interacting with cloudflare staff
doing so for the _root_ record is a bit dicier, but as x.com operates its own nameservers they're probably able to handle the not-quite compliant fuckery necessary to CNAME the root: https://developers.cloudflare.com/dns/zone-setups/partial-se...