That is like identifying the prime customers of a supermarket - people who live nearby.
Having customers who are particularly keen or invested for whatever reason does not make an enterprise a cartel.
Breaking up this 'cartel' is literally going to mean that the best 4 web browsers won't get quite as much development effort directed towards them. The plan seems to be to choke them of so much development that even dodgy hobbyist projects can complete. That is a low-quality bar.
Just ask yourself this: Google is one of the largest and most profitable companies on Earth. They are a for-profit, capitalistic company. Legally, their main duty is to maximize shareholder profit. Why would they give away somehting for free, if in the end, it does not benefit them more than not giving it away for free?
Competition is always better for consumers, unless you believe in a "benevolent dictator" situation (which, as reality shows, also never ends well).
People expect web browsers to be provided for free, which heavily complicates funding.
There is nothing stopping someone from making a new browser. The base of Chrome is open source, you don't even have to do the hard part. And distribution worldwide is relatively easy, if you can give people a reason to use your browser.
This comparison does not make sense?