Neither of those mentioned is on YouTube, and neither of them could survive on that alone. The Croatian streamer didn’t have to pay rent (her parents owned the apartment), and the Australian one has a partner with a job (but his job alone would not be enough). The Australian one would be closer to make a living wage, though (again, unusually high donations).

A big part of streaming on Twitch or Youtube streams is donations from fans and subscribers/members (regular payments from fans). Royalties from advertising is a part of it, but a lot of the money comes in from donations. Another common approach is merchandise in the from of stickers and clothing, people love that stuff.

You can do well even as one of the smaller streamers if your community and other monetization is strong. I've never really gotten why people donate, especially to the bigger streamers since it's clear they already have money. But it's a big part of it. You can easily watch hundreds of dollars in an hour get donated to even to a smaller or mid level streamer.

I don't know what you consider an average person vs royality, buy yes, there's quite many people I'd consider "average" that makes their living from Youtube - most seem to be starting at around 50k-100k subscribers before it becomes feasible.