Microsoft dominated with IE back in the day for the same reason Chrome and Safari are the dominant choices. People don't tend to change the default if it works okay enough. Firefox dropped heavily years ago as the market was saturated with other new choices already installed on mobile and Chromebooks, but recent numbers are about the same as they have been for a while. Maybe even still growing, as all the numbers I find are percentages, and there's no doubt we've had an explosion of device use.