Market forces are not effective at creating good outcomes when there is an oligopoly.
If there are two producers each with ~50% market share, it's not profitable for one of them to improve their product such that they capture an additional 5% of the market but reduces the profit margin of their product by 10%. If there are 50 producers each with ~2% market share, one of them would happily capture 5% of the market (more than doubling the size of their business!) by sacrificing 10% of their profit margin.
In the Google-Apple duopoly it's much more profitable to engage in tacit collusion than it is to defect.
If there are two producers each with ~50% market share, it's not profitable for one of them to improve their product such that they capture an additional 5% of the market but reduces the profit margin of their product by 10%. If there are 50 producers each with ~2% market share, one of them would happily capture 5% of the market (more than doubling the size of their business!) by sacrificing 10% of their profit margin.
In the Google-Apple duopoly it's much more profitable to engage in tacit collusion than it is to defect.