Well, until the 20th century, the modern way of funding science (by competitive grant proposals to funding agencies) didn't exist. Scientists were to a large part just doing it for love of the subject as being a professional scientist just wasn't a thing. At best they could get a job as a professor, but that literally meant teaching back then; if they wanted to do research, they had it do it on their own and pay for it themselves. And the best scientists of the era like Darwin and Lord Rayleigh were from the idle rich who never needed a paying job at all so they could devote themselves full time to science. It didn't work that badly -- except of course that the number of scientists was tiny compared to now.