iPhones sell massively well though, to the point where it would be a big loss if Apple went to another company for their screens. You just can't screw with a company the size of Apple without consequences. It's not like they'd go "oh no, no more iPhone now I guess :'(" if Samsung decided not to sell them screens anymore.

The problem is more with smaller companies that could be destroyed before they even get a chance to compete. Those can be bullied pretty easily by a company the size of Samsung.