Then they had to monetize. All those amazing courses are now gone (or "legacy" and nigh unreachable). Coursera is a sad shadow of its previous self.
These are generally any class that was niche and traditionally taught. I.e. a philosophy class that covers prolog.
Classes that are alive since ~2015 or earlier are usually remade every year or two to be more like a video introduction and are in a theme of either universal interest or that is mandatory for a particular degree (the first being good for bringing in new users and the second being good for certificate income.)