A new entrant would be unable to secure the investment, because even if he would produce the exact same piece of hardware with the same quality, the carrier distribution channels, the brand-image and (walled garden) ecosystem of Apple will prevent users to even notice and adopt the product, and the press would jump onto it and rip it to pieces.
So how would this normally work?
--> You disrupt the market by doing something particularly good, while being average in other areas, succeed, then iterate.
But this doesn't work in the Smartphone space as:
1.) iOS users are unlikely to leave their ecosystem because they can't take _anything_ with them
2.) the Google ecosystem leaves little room to disrupt and secure return-of-investment, and
3.) for Android you need to (re)build your own ecosystem to _match_ Google/Apple from the start.
That's why it's not a competitive market anymore, and needs to be (wait for it:) regulated to restore an even competition field for Hardware, Applications and Services.
But yeah...not a popular opinion here, I know...