Facebook will adapt to as many global regulatory approaches as it has to, and there will be dozens of them at a minimum that will be major markets and require compliance. The world is going to get very, very messy when it comes to complying with all the various approaches nations will implement (to speech broadly, politics, commerce, privacy, you name it). The compliance will act as a tax on its fat margins, basically.
It will become nearly impossible to form a new global social network as these rules come into being. No other entities will be capable of dealing with it, you'll have to have vast resources to do it. It won't be about paid vs ad supported approaches, that doesn't matter for that purpose: the localized compliance will go far beyond privacy (that is merely one issue on a long list of compliance requirements that will exist in the future, it'll be as complex and varied as cultures and government systems are).
The solution is to have local networks, then you care only about the local laws. Like on reddit each subreddit has it's rules, you have to respect the local rules , but you can participate in any subreddit
Microsoft hosts for example in Ireland (part of the EU), but is an American company.
A subreddit has its own moderators and rules, but has to also adhere the global Reddit policy.
FOSS is developed by people all over the world.
One solution is to lay low and be low profile. For example, an invite-only system, or E2EE. Another is to host in a more liberal country. But if the website is in Russian, it is assumed that its being served for Russians (people in Russia).
Comparing those two numbers (removed fake account, and FB userbase) does not give you reasonable insights.
FB ususally reports DAU/MAU (daily active users, weekly active users). That means, if you remove 500 million of not active users (not using facebook last month), these numbers are not affected. I don't think this would explain the majority of 500M number.
Most of the 584 million removed fake accounts were most likely created in the same period (and most of them were removed quickly after registration -- as said in the FB report). So they didn't decimate their user base, but additional 500M accounts that were deleted (so they shouldn't affect the user growth). This assumes vast majority of active fake accounts will be blocked.
It will become nearly impossible to form a new global social network as these rules come into being. No other entities will be capable of dealing with it, you'll have to have vast resources to do it. It won't be about paid vs ad supported approaches, that doesn't matter for that purpose: the localized compliance will go far beyond privacy (that is merely one issue on a long list of compliance requirements that will exist in the future, it'll be as complex and varied as cultures and government systems are).