This may be more regional-based and profession-based though. Around 2010 when Chrome was entering the market Firefox had around 30% global market share. In Slovakia where I'm from Firefox was "mainstream enough" that we had it pre-installed on high school and library computers and were taught to use it instead of IE as early as 2005..., But also in lots of enterprise-style managed companies (including basically all government offices, banks, ...) you couldn't use anything other than IE as late as 2016 cause there was no way they were gonna allow you to change your homepage from the company intranet home, so there were also lots of people who were using Firefox at home but also using IE at work because they had no other choice...
I think Opera had even bigger share in Eastern European countries at the time. But it was actively killed by Google. From homepage ads on google/youtube to blocking features or whole applications based on user agent.
This may be more regional-based and profession-based though. Around 2010 when Chrome was entering the market Firefox had around 30% global market share. In Slovakia where I'm from Firefox was "mainstream enough" that we had it pre-installed on high school and library computers and were taught to use it instead of IE as early as 2005..., But also in lots of enterprise-style managed companies (including basically all government offices, banks, ...) you couldn't use anything other than IE as late as 2016 cause there was no way they were gonna allow you to change your homepage from the company intranet home, so there were also lots of people who were using Firefox at home but also using IE at work because they had no other choice...