A lot of this situation is rather complicated, but I will try to write a little of what I know.
1. This is dry season, and fires are common, not just human-started ones, natural fires are common too, fires do have a role in the ecosystem.
2. A lot of the alarm raised by the media is more due to the hate on the president than for good reasons, for example people are using as number of the "increase of fires" comparisons between 2019 and 2013, but 2013 was a year where the amount of fires was particularly low, there was some recent years where the number of fires were just a little behind the current number, and the current number is still waaaaay smaller than what it was some decades ago.
3. It is illegal to clear land using fire in Brazil, usually the ones doing it are tiny farmers that don't have resources to clear land the correct way, or megacorporations that don't care (Cargill is a common culprit, not saying they are the ones at fault this time, but often they are).
4. Brazillian laws are kinda loopsided in ways that incentive people to do some weird stuff, for example brazillian environment laws are MUCH, MUCH harsher than other laws, this actually decreases compliance, because getting caught is so dangerous compared to some other crimes, that doing other crimes to not get caught is incentivized, there was a infamous case of a mayor of a town that just outright murdered cops because the punishment for murder was smaller than the punishment he would get if the cops managed to get to his property and investigate it.