From the outside it looks to me like Apple started reinvesting in Safari in 2023 (starting with adding support for notifications for PWAs) when the EU started getting serious about regulating the App Store monopoly, and they see investment into Safari as fodder for negotiation with governments about "people can always use the web if they don't like the App Store"
At WWDC 2007, Steve Jobs introduced a "sweet solution" for developers who wanted to program the iPhone: web apps in Mobile Safari!
Developers, who wanted a real, native SDK, were greatly disappointed (to put it mildly), and in 2008 Apple introduced not only a native iPhone app SDK with developer tooling but an entire app store.
But Jobs wasn't entirely off base. Gmail had replaced dedicated email apps. Apple had implemented native-like widgets in Mobile Safari as well as touch input, javascript canvas support, and audio support. Today you can implement a video streaming client (Netflix), game streaming client (Amazon Luna), groupware client (Discord, Slack, Teams), or even a whole office suite (Office 365) in Safari. Even many "native" mobile apps are basically just shells on web apps.
