This is not a benefit of the App Store but a benefit of a tight boot chain that largely prevents persistence.
No, it's a benefit of the fact that side-loading (the most common malware attack vector on Android devices) is not possible on iOS.
Sideloading is totally possible. It is just ordinary customers don't have the right to do so.
I suppose that depends on how exactly you define side-loading. I'll go ahead and clarify that I meant having a platform-sanctioned method of bypassing the default app store and instead downloading and installing third-party apps from the internet. But I think you could probably tell that from the context of the sentence.
But the fact that all app distribution goes through the App Store means that malicious apps can be disabled once discovered, and bad actors can be banned. This is important.
If you compare the situation on iOS to the situation on Android the difference is night and day.
https://arstechnica.com/information-technology/2020/04/solve...
https://www.theverge.com/2019/7/10/20688885/agent-smith-andr...
https://www.kaspersky.com/blog/skygofree-smart-trojan/20717/
https://arstechnica.com/information-technology/2016/07/virul...
This type of malware is far more pernicious than an app getting snuck past review, for example rooting your phone and burying itself so deep it survives factory resets. And all of these examples were distributed directly via the web or from third-party app stores, so Google can't simply remove them from the Play Store either.
If you think the App Store has a spotty record when it comes to malware I wonder how you'd describe Android or Windows.