Ask HN: How do online utility sites like YouTube downloaders make money?

Whenever I need to download a youtube video I got to a site https://y2mate.nu/en-FzLi/ . How does a site like this make money? Is it purely based on ad revenue, and how much can a site like this hope to make. I understand a large part of the answer is dependent on what traffic the site sees but I sometimes wonder whether they are profitable.