> I wonder if the existence of such giant monopolies is more of a symptom or result of a non-functioning capitalist system.

I think it’s a simple confluence of the US having many English speaking people with lots of money, plus English is spoken worldwide, plus labor is readily available in the US.

There exists buyers, labor supply, and the inherent ability for software to scale with very low marginal costs means targeting the US market results in a higher probability of success.

Once you can grab the rich US market, you now have the momentum to grab other markets, and being first is more important than being better where network effects are in play.