Yes, Firefox usage peaked at about 20%: surely not negligible (didn't know anybody myself using it !). As for geographical distribution, I could only find this: https://gs.statcounter.com/browser-market-share#monthly-2009... The data goes back up to 2009, which was quite a peak period for FF...

Sure FF has played an important role in the browsers war, but it hardly broke the monopoly, or at least it did not do it alone (Safari and Opera started to gain a significative share at the same time).