To the best of my understanding:
The smoke in Sao Paulo was from the Pantanal (much closer than the Amazon).
It hit a cold front and darkened the sky for a couple of hours.in the city of Sao Paulo on last Monday, and ended as conditions changed.
This seems a clear explanation from a poster (Rokatoo) who has always posted good/accurate info.
https://www.tripadvisor.com/ShowTopi...Sao_Paulo.html

In the Amazon, the subsistence farmers burn every year to farm and have been doing so for decades.
Other interests also burn for increased land for cattle.
President Bolsonaro apparently supports an increase in land available for cattle, to better the economy (and perhaps his bribes/political contributions fro rich buddies). Apparently the burning has increased this year because of his support and because of dry conditions.
https://www.bbc.com/news/world-latin...udvj_M_aLNCb70
Some think the amount of burned off jungle is rapidly reaching a tipping point.
IMO it is a national and international tragedy, but it is very far to the north.