There's an argument to be made that the extreme breadth of scope that modern web browsers are obliged to support (in order to gain/retain market share) heavily contributes to there being no worthy contenders against Chromium's web monopoly.

https://drewdevault.com/2020/03/18/Reckless-limitless-scope....

When you're the leader, you can further widen your lead by bolting on additional functions & features that require at least X amount of effort to implement. Any new contender will have to put in SUM(X effort for each feature) to match feature parity with the existing leader, and existing competitors will have to put in at least X effort to catch up. Existing OSS work can help bridge the gap, but only for what's already been done.