Do linux and privacy focused consumers actually make up a large portion of their market share? Linux users still make up a small portion of desktop users, and not even all of those really care much about privacy.
But they're the people friends and family ask for help when deciding to buy a computer. It's why Intel has slumped. Most people don't know what a CPU does, so that's not why they're picking Intel or AMD - they're choosing based off recommendations from more knowledgeable people.
For many years AMD was uncompetitive compared to Intel / Nvidia. Intel had 80% of the market at one point. It probably would have died off if it wasn't for folk that wanted Linux compatibility. Many run FOSS because of privacy. Linux is a key part of that.