Indeed, people are burning more this year than they did in the past few years – any burning at all has always been unacceptable, but if the current spike is what it takes to finally create some international outrage and put pressure on Bolsonaro, then I'll gladly take it.
It's a traditional farming practice that has been used all over the word https://en.wikipedia.org/wiki/Slash-and-burn
The idea is that you can burn a small place, cultivate it for a few years and then abandon it so the natural grow of the forest regenerate it. And some years later repeat the cicle.
When the population is small it's fine because the time between burn and burn was enough for the soil and forest to recover. When the population increase the time gets too small and the forest has not enough tome to recover, and after a few cicles you have problems like reduction of fertility, erosion and desertification.