I think the biggest reason Facebook became so profitable is that it built an extremely effective advertising system around identity, scale, and user behavior. Having real identities definitely helped with targeting and measurement, but Facebook’s business model was not primarily about simply reselling individual users’ personal data to advertisers. The bigger advantage was being able to let advertisers target specific audiences using signals Facebook already had, while keeping the actual user-level data inside its own platform.
I also think Facebook benefited from having massive reach, strong engagement, and eventually Instagram, Messenger, and a very mature ad auction system. Other social networks either never reached the same scale, had weaker targeting data, or struggled to turn engagement into an advertiser product that could reliably produce measurable sales.
Do you mean profitability compared with platforms like Twitter/X, Reddit, and Snapchat? I ask because each of those had very different problems with monetization, so the comparison gets pretty interesting depending on which networks you have in mind.