Lol, you're talking as if it's unique to Facebook. Anyone with money and a modicum of technical expertise can make a messaging platform. The hard part is monetization.
Most people in the world actually don't use Facebook for messaging. Messenger is second to WhatsApp.
There are dozens of software that can do worldwide instant messaging. It's ridiculous to think that that's why Facebook is successful. It's not, monetization and network effects are the reason, not being technically superior.
Ubiquitous universal communication. It is the stuff of utopian sci fi.