Why is Facebook so profitable while other social networks aren't?

Meta owns Facebook, Instagram, Messenger, and WhatsApp. Billions of people use these platforms, generating vast amounts of time spent and interaction data; consequently, high profitability is a natural outcome.

"The Boomer factor"

Facebook built the most advanced advertising engine and tracking Pixel in the market.
Because people use real names, connections, and local behaviors, Meta’s ad machine can accurately map user intent and micro-target audiences

i think the amount of real user data + how mature their ad system is probably plays a huge role. the targeting is just on another level compared to most platforms

In my opinion, Facebook has a massive global influence, and anyone can access it and earn money from it legally.

Facebook has a large user base, which gives advertisers access to many people. Its advertising system can also help businesses reach specific types of users. Other social networks may have users too, but they may not have the same level of audience size and advertising demand.

Actually Facebook have lots of real facebook users with various category. So Facebook gets data from these users like their interest of buying, Interest of niches etc. On the other hand the Business owners are targeting with their paid ads by using these data also Facebook helps now by using AI Technology. So the business owners gets sales/ leads from business ads. This is the main reason facebook are now more popular than others social media.

A big part of it is simply scale. Facebook has a very large and active audience, so it can attract more companies that want to reach potential customers. Its long history and strong user activity also give it an advantage over smaller social platforms.

Because fb is popluar social media and people spending hours on fb

One angle nobody mentioned here — Facebook is basically the internet in large parts of Africa and Southeast Asia. In Kenya for example, most people access Facebook through the free tier of mobile data plans (Facebook Zero / Free Basics). So for those markets, Facebook isn't competing with other social networks — it IS the social network, often the only one people use daily.
From a media buyer perspective, this matters a lot. When you run FB ads targeting emerging markets, your reach is massive compared to any other platform. TikTok is growing fast in those regions, sure, but the purchasing power audience (25-45 age group with mobile money wallets) still lives on Facebook. The targeting data Meta has from those real-identity profiles is just miles ahead of anything else available for tier 3 GEOs.
That's also why FB ad costs in those regions are still very low compared to tier 1 — less competition from advertisers but huge engaged audiences. It's one of the few arbitrage opportunities left in paid traffic.