[perihelions]

> "why don't those rich people make space telescopes just for fun?"

They do! You can look up why the Simonyi Telescope, or the Sloan Digital Sky Survey, bear those names. (Two examples from memory; there's many others). (edit: Or the Allen Array, for Microsoft fans)

The world's largest telescope of the mid (20th) century was a Rockefeller donation. Several of its peers were Carnegie's.

Observational astronomy was, for much of history, a useless hobby for kings and idle rich. It's a very recent thing that democratic societies decide to fund this kind of no-applications research through public institutions—and to do so on the megaproject scale. There are no precedents in human history for JWST.