Well, those stats are wrong, because a lot more than 1% of browsers are on mobile platforms with no WebGL support.
Of course there are more than 1% browsers that support, but we're talking about implementations, not devices. You can can have an old iPhone running iOS pre8 and it won't run WebGL, but one can say that iOS does support WebGL now.
The actual implementation stats are here http://caniuse.com/#search=webgl
So firefox is a class, and there are instances of that class running. Most instances are running on mobile devices, so it really makes sense to say that only a small minority of browsers are capable of running WebGL.
WebGL was enabled on Android on KitKat, and according to starts, that's 70,8% of installations (http://developer.android.com/about/dashboards/index.html)
WebGL was enabled on iOS on 8, and that's 93% of installations (https://developer.apple.com/support/app-store/)
I'd say most of mobile browsers can run WebGL, it's just that the experiences are not designed for mobile platforms (this Polygon Shredder, for instance, it does work on mobile, it's just too slow to be good, but I can probably make it work)
Other experiences like https://www.clicktorelease.com/code/cruciform/ or https://www.clicktorelease.com/code/xmas-virus/ are supported and do work as expected.
You're right that there's a lot of phones that are too underpowered to run WebGL experiences, but the browsers themselves do support it perfectly.
What version of Firefox, OS, GPU, etc. are you using?