I wonder if the existence of such giant monopolies
is more of a symptom or result of a non-functioning
capitalist system.
The world, at least the western world, desperately needs viable mature competition not based in the US.
I would go so far as to say not having it is a real problem for democracy and maybe even go as far as it being an issue of national security.
With the close ties between intelligence services and social media in the US, it is a problem for the US, but certaily more outside. However it is a challenge to avoid 5 eyes.
Less conspiracies, two rich and powerful persons in the US can decide what information is permissible in an election and what is not.
This would not matter much, if there were at least 10 different healthy competitors with at least a few million users.
Hopefully being more distributed also internationally, it would be unlikely that each leader would make the same decisions.
Like newspapers, they can suppress a story, but another newspaper might go with it.
Sadly in the US, the mass death of newspapers often means that a region / city /state might only have one newspaper in a monopoly situation.
I do not know if the state injecting billions can get to where we need to be.