The farm I'm on has basically doubled its cattle numbers over the last fifteen years or so. Effectively they are now barn raised whilst the fields they used to graze now grow the high protein supplements in the form of beans & peas instead. The barn slurry is now pumped and distributed to all the fields: even travelling under roads, in large gauge pipes then to a trailing hose direct to the tractors. In some respects its efficiently done and keeps the manure cycle going: obviously in other ways its not ideal.
I think the key to the issue in Brazil is fast money from logging. The cattle ranching and soy/ palm oil comes later, but it only takes a few years (a presidential tenure...) of cutting three hundred year old legacy hardwood trees to make those controlling the operation very very rich.