It did, but did it ever _have_ to be?

Nothing ever _has_ to happen; that implies intent in markets.

Efficiencies and user experience are better for more users on social media than email, despite it's obvious flaws.

Did regional steel mills _have_ to replace local blacksmiths? No, but they did.

If you where sent into the year 2000 with a mission to prevent the adoption of social media and instead maintain Email's dominance, what would you do?

Build an open messaging protocol and decent clients. Oh wait, some did exactly that.

The problem sadly isn't tech related. It's education. Corporates will market to the masses who are mostly tech ignorant, if not politically and economically ignorant too. So even with alternatives, the power of commercial communication is greater than what non profit are able to afford.

We will have to wait for people to suffer further and further, more will open their eyes to it, until radical resistance settles in people's limbic systems. We are getting close I think, I hope.