It’s a little more complicated than that. It’s not just a question of market share, but whether you use your market share to make it impossible for others to compete against you.

For example, Microsoft was getting itself into trouble in the late 90s because they essentially used their dominant position in the OS market to push Internet Explorer— making it next to impossible for other browsers at the time, like Netscape, to compete. For example, they made it difficult for other companies to install their software when their own competitive alternatives were included for free, and in some cases, impossible to remove (explorer was fully integrated into Windows at this time and you couldn’t remove it).

There are plenty of companies that essentially own entire markets. Google for example something like 85%. There’s nothing wrong with that.

it still boggles my mind how people don't understand how a company having a monopoly isn't a good thing. prices go up, innovation goes down because you have no options.

iMessage is vendor lock in, not being better. Apple is just as bad as 90s Microsoft on vendor lock in and EEE.

Being successful isn’t illegal. But using your success to stamp out the competition is illegal.

You cant. Thats just cause people dont understand anti trust law. You can absolutely have monopoly by competition. If you win the market the government isnt gonna stop you.

Antitrust measures are when you actively take away ways of competing. Like if apple paid carriers to not sell androids.

It's the only reason Apple even exists today.