Of course, Brazilians speak Portuguese because Brazil was colonized by the Portuguese, but why didn’t they conquer more? Uruguay? Argentina? They were right next door!
It all goes back to 1494 and the Treaty of Tordesillas proposed by the Pope.
This treaty divided the trading and colonizing rights for all newly discovered lands of the world between Portugal and Spain. This way they would avoid rivalry and possible war as each nation prepared to send ships of exploration.
Basically the from the “tordesillas meridian” to the right was for Portugal and from there to the left was for Spain, talk about getting a small slice!