Fast forward to today. What'sapp is the dominant messaging application across the world. Carriers hate it but they can't do anything to stop it. Facebook hates it and no matter how much they improve facebook messenger, they keep falling behind.
This represents a massive existential threat to Facebook's business: engagement. To kill their closest competitor for, again, less than 15% of the company, is a rational decision.
Since Viber and What'sapp have both exited the market, I think it's time for someone to build a new messaging app. There's a lot of room in a once incredibly crowded space.