Realistically I don’t actually because I’m not rich enough and have no idea how start and run a company.
The current mobile market is locked-in and 10 billions wouldn't be enough to create a competitor.
Instead it's a demonstration of the power of two-sided markets. When Apple came out with the Apple ][, Silicon Valley had a competitive advantage in electronics because of networks across firms. Need parts? Need specialty talent? You got it.
Now the "competitive" edge of Silicon Valley is that it is the home of great monopolists such as Facebook, Apple and Google. That is, it crushed the competition and prevents it from emerging.
There's also the reality that (1) brands feel the need to express their brands through apps, (2) they are already annoyed enough that app development cost is at least doubled because you have to support iOS and Android, (3) many would express the belief that being forced to develop apps for a third (fourth, fifth, ...) mobile OS would be "extortion" or the equivalent. My understanding was that Windows Phone went EOL because carriers in the US were refusing to activate them because they too think it is bad enough to have to be able to deal with two OS.
If Android didn't exist, however, you'd probably being paying less than a 30% rake to the app store because the App Store would have been seen as a monopoly and the court would have done something about it. As it is the zombie OS Android doesn't really make money for Google or anybody else (Samsung is just proud it makes phones) and wastes money for app developers but it does make money for Apple. From that perspective a third mobile OS is like a fifth wheel.
There is such a thing as "pernicious competition" where fake competitors prevent the entrance of a real competitor, for years cable TV was a great example because you'd see several cable operators, several satellite operators, and later several IP based operators that all offered the same crummy channels with the same crummy UI at the same high price. Not only did the cable operators not serve the same customers but the structure of the industry caused them to "collude" to offer customers the same thing.
Android is like that. It adds $10-15 billion profit a year to the Apple App store just by keeping the court away.