Selling user data, selling ad placement, subscriptions for paid services, enterprise-grade support contracts, and the like.
They could also take an approach similar to Google, branching back out from being just a browser into a suite of related tools that Chrome can then convince users to switch to (similar to how Chrome gets users to not just use Google search, but also services like Gmail too.)
According to this great reporting by Protos, he holds over $580,000,000 in just Bitcoin, with tens (and sometimes hundreds) of millions in other assets, like TRON (the coin you can see promoted on the side of his microphone in the article's photo) which is a clone of the Ethereum blockchain he made by simply copying the code, artificially lowering fees, then publishing it as if he created it.
Not only is he a rich douchebag, but he's also a plagiarist.