First of all, Linux is not a desktop environment. If you meant “desktop operating system” in that statement, there are still a lot of problems with that.

Windows does have a lot going for it, wide app support, ubiquitous use in industry, and the backing of one of the biggest tech companies in the world. But for most people, linux has enough app support for their workflow with only minor modifications.

Email, web browsing, and office apps are all that a vast majority of people use their computers for. And all of these work “out of the box” in all mainstream linux distros. It just looks different than what people are used to, so they are hesitant to try it when offered, but can usually find their way around given a little instruction and time.

Look at chromeOS as an example, definitely not your traditional linux OS, but still runs on the linux kernel and has all the issues that come with that. However, chromebooks are still one of the most popular laptops for use in high schools. Schools may have ulterior motives for this choice of device such as surveillance, but the devices still work for 99% of what those students need for their classes. And a traditional linux operating system is even more flexible.

There are some apps that the libre alternatives are objectively worse (photoshop and CAD software come to mind), but people that use these kinds apps are a minority of desktop users. And support for them would likely increase significantly with more users moving to linux, making the area more profitable for companies to support.

We are all biased towards what we are used to, and that means that I am biased towards linux. However, from my experience helping others learn how to use linux, they generally don’t care all that much. For personal computers, the biggest concern they usual have is about games working, but those issues are getting easier to fix by the day

No, part of the antitrust requirements would likely be them having to stay out of the browser market for a set number of years.