well, tbh I would say that fb is king here because telcos offer access to fb and fb messenger free or at very reduced rates along with your phone load, which is cheaper than buying data/total internet access. the majority of the population can more easily afford fb access and can't afford data.

Ph social media usage might look very different if it wasn't artificially swayed towards fb in that way, imo.

Yes! Very good points! Free access, and Messenger is a big factor as well why even kids who are not supposed to be on FB (as per their Terms) have accounts (regular accounts at that, not the "for kids" version). FB/Messenger truly cornered the Philippine market.