Google works this way (and I probably am getting parts wrong):

Advertisers classify their ads a particular way (e.g. sports, politics, etc)

Websites classift their sites a particular way (e.g. sports, politics...)

Google matches ads in a category with websites (sports with sports, politics with politics). As far as I know there is no further screening. Then again I am no expert, but I use Google ads on my newsletter site.

When someone clicks on a Google ad, the person advertising then pays the website some small amount. If you want to see what Rudy or Ann are up to and you click, they pay Liza. There may be other kinds of ads too where simply the presence of the ad pays Liza or ads where only if you buy something does Liza get a cut. But Google ads are usually pay-per-click.

Again, if you don't advertise you are much more limited in the time you can put in. Liza puts far more into this than any of the rest of us do so for her it has to be a business. People like Holland and Wallner who complain could a.) give her some of their time to help with tech stuff, publicity, etc, or b.) pony up and pay Liza some cash so she can have more options. Otherwise how can they complain since they are getting a free ride?