Comment by ZeroGravitas

The market has likely grown by a large amount in that time, and a big chunk of that growth will be on platforms that either ban, or strongly tilt the user's choice of browser.

That and the competitors being rich corporations that are happy to pay to convert low-information users probably accounts for most of it.

I've not looked recently but looking at actual user numbers has long told a different story, which no great decline except in relative terms when compared with rivals.