Bitcoin is currently a success in the same way Linux is/was a success: in a very tiny niche (geeks, sysadmins, tech-savvy folks, etc ...). Unfortunately, Linux never came out of that niche. It's still in there 15+ years later
You do know that 80% of the internet is run on Linux machines, right? This very website is probably sitting on a RedHat server or at least something Debian or Ubuntu based. And it's the most widely used OS on mobile (Android) world-wide. Add to that every game console uses a Linux kernel (If I'm not mistaken even XBox does). In regards to desktops/laptops, yes, small market share.