[evgen]

All of those so-called challengers who died were ones that basically were killed by Facebook in its rise to power. None of the 'global competition' is really competitive outside of China, and the new entrants are copied as soon as they come out with something interesting. New challengers may emerge rapidly, but unless something is done from a regulatory side those same challengers will flame-out into either death or mediocrity within a few years of appearing.

As a simple example, those 'new entrants' (can we really call any of those four new other than TikTok?) are all multi-billion dollar companies, but by quickly cloning the interesting features of those entrants Facebook probably siphoned off as much value from those entrants as they are now worth. In a world without Facebook copying them all four of those companies would have market caps that were at least 2x their current levels.