[ethbr1]

Netscape? IE didn't become dominant until 2000+.

And those four players are more of a cartel than competitors, having agreed to mostly stay out of each other's ways.

The primary overlapping markets between them are consumptive devices and cloud services -- which I presume they're all in because they consider it strategically important enough to their other businesses to incinerate money.

[adrr]

Apple and Google makes phones. All of them make tablets. Microsoft and Apple make laptops. All but Apple sell cloud computing. Google, Apple and Microsoft have office suites. Apple, Amazon and Google offer paid streaming platforms. Amazon, Apple and Google All offer smart assistants. I can keep going with things like game platforms, consumer storage,streaming music. Failing to see how they stay out of each other's way or have agreements with each other. Apple and Google literally give away their office apps which is the bread butter of Microsoft,

[ethbr1]

Apple and Google don't compete on phones, because they've each intentionally built incompatible ecosystems.

See earlier comment about consumer devices.

Office suites have Google sharing an MS Office-compatible suite they purchased. Apple has MS Office on its platform. But no real competition or innovation.

Who aside from Microsoft runs a gaming platform?

What looks like open competition gets a lot narrower in overlap once you look at the details.

Which is exactly what you'd expect, if you allowed companies to get too big and too dominant: they're not dumb, so they strategically rig the game in their favor to disadvantage new entrants, while carteling with similarly sized peers to ensure everyone mostly stays out of each other's pools.