Microsoft, Amazon and Meta have plenty of “capital” and they couldn’t create their own ecosystem for their own phone and convince software developers. The hardware is not really an issue. Any company with a few million can sell their own phone and get a Chinese ODM to customize it for them and white label it.
Outside of Apple and Samsung (only because they make a lot of their own parts), the phone market is a commodity race to the bottom
Amazon, Meta and Microsoft tried their hand at making competitive devices and enter the market, to varying degrees of effort but practically identical degrees of failure. All this to say, it takes a lot more than just capital.