I'm Brazilian, and I'll explain a few reasons why there are so many players here.
1. Big national celebrities are influencing more and more people to start playing.
2. There are hundreds of teams in Brazil, all with hundreds of players. Poker has become a huge business in the country.
3. Our currency is weak. We're living in difficult times in our economy. Earning some USD is attractive. It's not difficult to earn 1,000 USD in micro stakes every month. This amount, converted to around 5,500 BRL, is much more than most people earn in a normal job.