How many good web "working" browsers has there ever been at one time? I submit it has pretty much always been one. That is there has always been a single browser that could browse the web really well and everything else has kind of sucked because it was poorly supported by content producers and has suffered technical limitations.

Since I've been using the web it has been: Mosaic, then Netscape Navigator then still netscape for me but a lot of the web shifted to IE, then Mozilla or ie depending on platform, then Chrome

...there hasn't failed to be competition (ie people have tried) but they have failed to get traction.

Meanwhile the complexity of the web and its underlying protocols has increased a lot, user expectations have shifted from static page viewing to running all manner of apps in the browser, and necessarily browsers have become more and more complex.