Original question being answered: Why is the s9 not able to run emulators that iPhone x can.
Sub-question - Why is the s9 so slow?
Emulators run very slowly - any emulator running in any computer. They turn a compiled program (in many cases) into an interpreted one - which is 50 times as slow or slower just because of that.
Add the fact that you're comparing the speed of an app running in the native machine code of an iPhone (that's how iPhones work) with the same app running in the interpreted Java mode of an Android (because that's how Androids work). So if you're running an iPhone app in an iPhone emulator on an Android, you have teo slowdowns - interpreting the iPhone code to something the emulator can run in a Java interpreter, and interpreting that by the Java interpreter in Android.
Now we get to the original question - because Android SoCs (Systems on Chip) can't run the same code as iPhone CPUs run. It's the same reason French people don't speak English. If there's an emulator, say for the PS2, that someone wrote for the iPhone, that would be running in iPhone machine language. If someone wrote a PS2 emulator for Android (and evidently no one did), it would be written in Java/Kotlin, so it could run on an Android and, since Java is an interpreter, it would run a lot slower.
You're confusing apples and cars - they're not even the same class of things. One is native code, one is interpreted, One is running in an SoC that's used for Android, one's running in a CPU made by (or, more likely, for) Apple. Why do apples fall on cars, but cars don't fall on apples?