Making it available via a static file host dramatically lowers the barrier. If you have an interesting dataset, you can even throw it on github pages and pay nothing; that likely is not true for your mongo db server.

A typical request using indexes will be less than 10 separate 1KB GET requests, not 50. But yeah, more work needs to be done on performance.

Whether it makes sense to fully download the dataset depends on the project; maybe it does not. But it doesn't have to be a monolithic file. You can use SQLite's multiplex VFS to split the SQLite file into many smaller pieces (and still update the db later!).