Agreed. Fintech is huge in all growing emerging markets, especially those driven still on top of cash. No credit card infrastructure to mess with - move right onto digital wallets. China is the obvious example.
I do not think the opportunity in Brazil, for fintechs, is about people using cash. More than 100 million have a bank account, with a card, and more than 70 million have a credit card[0]. Almost every place you go you could use a credit card to pay, including churches and street vendors.
But, is too expensive and too much bureaucracy to take a loan. Big Banks is one of the sectors that most profits in Brasil[1], so they do not care so much about small and personal loans. Or loans to small companies. And the legislation sucks too, politicians have passed a new law that will make even harder to make Angel Investments[2]. Is too risky and expensive for everyone that want to loan money to people. Loan money to government is more profitable and almost without risk to Big Banks and mutual funds. So, there is a huge opportunity to disrupt this.