Why doesn't anyone enter? It takes billions and billions of dollars, tons of knowledge and if you get it wrong...even Intel screwed it up, and they are one of the only companies would could even try to do it.
The sooner Intel spins out the fab side into its own entity the better positioned it will be to pick up the business that TSMC doesn't have capacity for.
People will overlook a lot, if the product is compelling enough and the sales guys can keep a straight face while promising not to peek.
Apple and Microsoft are trillion dollar companies ( both nearing $3 trillion market caps ). They can afford it. Heck they have the balance sheet to acquire both tsmc and samsung if either were up for sale.
I thought Apple was moving towards being a full-stack company. Where all the hardware and software is developed in-house. If anyone has the resources, it is apple.
Having a modern chip fab binds an insane amount of capital, and makes you much more vulnerable in case of market turbulences. This is exactly a reason why there exist people who like to claim that Intel should spin off their fabs.