It depends a little bit on how you look at it.
In the desktop sector, Linux roughly settles in at a 2% market share.
I wouldn’t necessarily say in this sector that Linux is so popular.Mac and Windows are far more “popular”.
The situation is different in the server area.While Windows Servers typically focus primarily on integrating and managing the entire infrastructure, Linux servers are more modular and easier to use as a special server.
For example, it is often easier to integrate Linux servers into a heterogeneous infrastructure (Linux and Windows clients mixed) than to teach Windows Server to befriend Linux clients (depends a bit on the purpose of use and my personal experience is there quite already 10 years old, maybe a lot has gotten better, even if that would surprise me).
Of course, it is simply also a question of cost.If I need 1000 servers, it makes a difference if I need 1000 Windows Server licenses (probably not, but alone to find out how much I really need, server licenses, CALs, etc., costs some time and if I am unlucky and wrong, I’m still in jail with 1.5 legs) or just install a Linux of my choice 1000x.
In addition, there are plenty of useful and sophisticated tools for administration under Linux also free of charge.Often I can choose between several variants and see what is most suitable for my situation. Many things that do the same for Windows servers sometimes cost money, and this is also quickly noticeable on many servers.
Modularity on Linux is better developed.In addition to a basic system, I install only exactly the software that the server needs for its function.
Since much of the open source is based on the KISS (Keep it simple) principle, most programs actually do only one task and nothing else.This often allows me to exchange individual tools if the previous one is not up to the task.
Often, I think, the documentation is better on Linux (larger community) than on Windows.However, there are exceptions…
My biggest annoyance was when I was still administrating years ago, the Windows servers in German.The German translation of typical IT keywords was so stilted and unreal that I really kept thinking about how XY could be called in English so I knew what they meant. We should have just bought English 🙂
I leave Android out here, as many of the advantages that Linux brings in itself are equalized on Android (for apps the sources are not necessarily available, i.e. I use closed source again, as in Windows; typical Android versions of smartphone manufacturers consist of open source shares of Google/Android and closed source shares of the manufacturer, etc.). And about security (this is often mentioned in Linux/Windows comparisons) you can also have a variety of opinions regarding Android.