Suggesting that Unix has been continuing just by inertia doesn't explain why Apple adopted Unix for macOS or why most newer computers nowadays run a Unix OS.

Apple did not adopt UNIX per se.

Apple failed miserably to create a new OS, decided to buy a company instead and they happened to get the one where Steve Jobs was.

NextSTEP was partly based on UNIX, because it was competing against Solaris and needed some compatibility for easing the port of applications.

It used a micro-kernel like architecture, drivers where written in Objective-C, the whole userspace used the Foundation libraries and the bundles concept, the GUI was based on Postscript engine.

All very little to do with what a UNIX is.

Also if Gassé didn't ask the crazy amount of money he did, Mac OS X would probably be based on BeOS, which didn't have anything to do with UNIX.

Apple took NeXTSTEP and with minimal changes had macOS certified as UNIX, so it is actually UNIX, unlike many UNIX-like operating systems.

I suggested nothing of the sort. I am criticizing your use of "still going strong" as proof of good design. And there are many possible explanations of why Apple adopted Unix. Inertia is certainly one of them! (If you want to write a new operating system, and all your programmers are familiar with unix, and you don't have enough money to start from scratch... you start from unix)

Intiertia among developers. Also since when is Apple know for their software architectural decision-making lol.

Apple didn't make that decision; NeXT did.