Caddy's appeal when I last looked at it some years ago was that the configuration file format was very easy to read and use; and that configuration itself was minimal. It came/comes with Letsencrypt integration which was novel some years ago, so setting up a secure site was even easier for people who weren't used to it.

Its syntax for being configured as a reverse proxy (secure front-end to less secure back-end servers) is similarly pretty easy.

I haven't looked at it in a long time because I recall them screwing with their terms of service so it wasn't fully FOSS by the most liberal definition.