Another important issue to realize is that it's a curse in Silicon Valley and in the capitalist world as a whole: Firefox doesn't need to be the market leader either. Surprise?
Right. Firefox can still survive and live well with the second, even the third browser position in the market. The fact that my favorite browser, Vivaldi, is hard to be identified on the market share map.
Is proprietary culture on the web bad? Yes, it makes the whole system easy to crash, but despite Firefox's market share is declining, the browser market still has no monopoly phenomenon.
When Firefox was released, Microsoft monopolized it by installing IE on every Windows machine. Now Chrome is also somewhat exclusive. But there is an important difference between IE and Chrome - Google does not ignore the web the way Microsoft does with IE, meaning that the role of Firefox today does not need it to have a lot of market share. Firefox can play a different role, providing an alternative for those who need it without having to worry about market share.