My take on it (and I lived through this) is that pre-web everyone ran on Windows. If you were writing software, it needed to run on Windows, so you had to code on a Windows machine.

Then the web changed things, and a huge number of devs moved from writing Windows desktop applications to writing web applications for the dotcom boom (I was one). This took about a decade, from around '97ish. It also freed people to use different dev machines because most of the servers were LAMP (or variants thereof), and Macs could run the AMP bit fine. Web designers who had started off in Apple-land being designers on Adobe migrated into being web developers, and that helped spread Macs into the web dev community.

Yes, Macs did get better during this same period, and there was a lot of great innovation. But if nothing else had changed then that wouldn't have mattered - if you had to write Windows applications then you couldn't do that on a Mac, no matter how sexy it was.

I find the parallel with today's situation (and this discussion) fascinating.