The impression that "
most of the action has moved to mobile" is just an impression.
First of all the market share of desktop versus mobile is roughly 43% for the desktop, 57% for mobiles and tablets. More importantly however is that the rise of mobiles has been sharp since 2009, but it's been stagnating since 2017 and this stagnation trend is clear. Mobile devices too are a commodity, their market isn't growing any bigger and people aren't replacing their phones as often. The market for the desktop did not shrink. It just reached saturation. And as it will become increasingly clear, mobiles have reached saturation too.
What devices do people use in companies to do their jobs? Laptops. Sometimes tablets, for drawing on them, although a piece of paper would do. Mobile devices have been and remain essential for communications, this meant phone calls in the past, nowadays it means WhatsApp, Slack, email, along with shitposting on Facebook/Instagram/Twitter, but that's about it.
> "webservers (where Linux is massively dominant)"
Sorry to disappoint you, but the market for web servers is actually small, unless you're Amazon and Microsoft realized at some point that selling Linux boxes on Azure is probably more lucrative than what they were doing. The web servers space was never Microsoft's so they had nothing to lose.
But the enterprise space is dominated by Microsoft, with their dominance only increasing. Exchange, Sharepoint, Office 365, Skype, Microsoft Teams, Azure DevOps, freaking Yammer, MS SQL, soon GitHub, their reach in the enterprise and their adoption, once you're familiar with the space, is actually quite scary.
I have to hand it to them, they became really good at marketing. Otherwise I can't explain this portrayal of them as being the underdog. Or the constant nagging messages I see about them having changed, due to them releasing VS Code or .NET Core.
No they haven't changed much. The tooling they make for developers has always been top notch and while .NET was proprietary, they standardized it and they never attacked Mono. Office has been available on Macs since 1989. And they no longer target Linux with patent threats of course, they target Android instead. Until they'll find some way to sell Android. They adopted Chromium, a master move since now they can cut some development costs and win back some users and sell them on Bing too. We'll probably see them windowfying Android too.
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Note that I do enjoy several Microsoft products. But I'm always skeptical when hearing about their motivation. I don't understand what makes people cheer for these big companies, as if they are sports teams. Use their products for what they are and dump them as soon as you find something better.