Firefox has been the standard for years after IE. Then Google invested huge resources in pushing Chrome and succeeded because they released at the right moment a super simple and optimized product compared to the huge behemoth Firefox was becoming. Things are quite different though now, and FF can fight Chrome in the same league speed wise then win hands down when it comes to privacy. Turning the tables back is definitely possible, but won't be easy or immediate though due to the amount of resources Google can invest in advertising for its products, which are orders of magnitude bigger than what the Mozilla Foundation could use.