The podcast Blank Check goes into it while talking about the movies, but that's admittedly "long form". Wikipedia has a good summary.

In short, George Miller was an Australian ER doc horrified by what cars can do to people. So he got some funds together with some other doctor buddies and made Mad Max. He and Byron Kennedy wrote and filmed it because they couldn't afford to have someone else do it. Mel Gibson was a local guy in film school. Most of the cast doubled as crew and basically made their costumes from scratch themselves. It became a bit of an indie darling in the US and Miller went back to Australia with more money and more expertise and made Road Warrior. More or less the same happened with Thunderdome. His work partner died, he made the Happy Feet and Babe movies, and he retained the entirety of the rights to Mad Max so he decided to make Fury Road and Furiosa a few decades later.