People do have difficulty switching between Mac and Windows, but each has critical mass so it's still easy to get help with the finer details. And unrelated to fragmentation, anyone tech literate won't have nearly as many showstopping issues to ask about there in the first place.
Really? And windows does?
If you're not convinced: look at the difference between desktop Linux and Android. Although Android Studio seems to be a bit of a disaster nowadays, there's a lot of development support for Android, and it shows in the 1.6 million apps that have been built for it. Android has got what people crave: easy, slick, user-friendly apps, no technical hassle. It's an uphill battle, and at the same time, the focus is shifting away from desktop. So I think the year of Linux for the desktop will likely never come.