Comment by Sylos

It pays off for Google to develop Chrome, because:

* they can feed Chrome Sync data into their advertising databases.

* it means that they don't have to pay other browser vendors quite so much to make them the default search engine.

* they can take control over webstandards for their other profit-driven purpose.

* they can hinder the blocking of their ads.

Mozilla can't or chooses not to rely on any of these profit schemes, so they need other ways of making money.