Most people don't choose a browser based on principles or mission. Even if Firefox captured 100% of the market that did, it would barely move the needle in browser share.
Most people choose browsers based on fairly straightforward things, such as the default (many people never change this, which is why changing the default browser via bundled downloads has remained such an effective marketing strategy for decades), performance, the feeling of performance (which is different from actual performance), whether the websites they're visiting are supported, etc.