Almost none of that is true.

> Computers has much more legacy code to support and that create a lot of vulnerabilities.

Not necessarily.

> Also computers have to support much more protocols, which also create some vulnerabilities

What protocols do computers support that your phone doesn't? On the other hand, phones support many protocols related to cellular connections, texting, calling, nearby communications, etc.

> ios uses linux cores

Nope.

> which are more localized and have less attackable structure.

The Linux kernel is anything but localized, it supports many more architectures than Windows.

> But most importanly linux problems are much less known, because it became popular relatively recently and some thing maynot be found yet.

You say that as if you need 10 years to develop an exploit. Not even close, many exploits are found due to new features with poor implementations. In any case, I'm not sure how true the claim that Linux has only recently became popular.

The real answer is defense in depth. App Stores provide a much higher barrier to entry, you can't just build an app and release it, you must sign up to a developer program and sign your program (even then, there's no guarantee that your app won't be immediately blacklisted after being found to be malicious). Even on Android, users need to explicitly allow apps from outside of the Play store. In addition, every app is sandboxed and has limited to access to files as well as hardware and software resources. Pair that with an immutable, signed system volume along with signing and verifying every program that runs and it becomes extremely difficult to attack.

All of these tactics could be applied to PCs, it's just that some of them significantly limit the user's control of the PC (and thus the usability), while phones have never really had that freedom in the first place.