In the ensuing decades:
- VMs for development have become more popular. You can run Windows but then easily develop on Linux using VirtualBox. Virtualization is very popular now when compared to the late 1990s/early 2000s. You also have WSL and WSL2 and cygwin
- Windows sadly is no longer the development platform of choice. Production runs mainly on Linux. Since deployment is on Linux, its a good idea that development happens on Linux to iron out any subtle platform issues and also get good support for native extensions in languages like Ruby, Python, PHP etc. Some server software/middleware (message brokers, databases, caches etc.) have much better support on Linux. This necessitates again using Linux rather than Windows for local development
- Due to the rise of mobile and web applications, the dominance of the Windows desktop platform has decreased. Not supporting Windows at one time used to be unthinkable but no longer
- The Windows platform in the late 1990s was arguably technically superior and robust when compared to its competitors. Now Linux and MacOS are robust and very capable as well
- MacOS has risen to become important amongst developers
- Docker runs on Linux
All these factors have led to Windows not being a first class citizen for many open source projects.
> If PHP never ran on windows it would never have ever gain its popularity, it doesn't matter if it's then deployed on Linux servers.
This is a historical fact. The situation in 2021 is different. If a new language is trying to break onto the scene today it must support Linux first. MacOS support often comes "for free" because of its BSD heritage. Windows is quite different internally and due to the reasons above, often lags behind in first class support for many open source packages. Platform support at the end of the day is a "network effect" and the network is with Linux/Unix currently.