There's no magic, Browsh is just designed to be run on a remote server where internet is fast and cheap and then accessed over SSH or the browser client from a local network that is likely slow and/or expensive.

It runs a ‘real’ browser on the server and renders pages there.

The use case here is one where one has slow access to a machine with fast internet access, or where the local machine doesn’t have enough resources (e.g. screen resolution, battery live) to render web pages.

It goes through Browsh's proxy.

While I think Browsh is very interesting, you can immediately see a couple issues with this. When I tried it last week, it worked pretty well for a bit, and then I got an error that all the servers were busy.