From the article in the reference, the government intends to use these restrictions to fight fraud and money laundering. They claim they intend to fight underaged gambling and protect its citizens from fraudulent gambling platforms. This is the right step that will help the country combat crime and citizens' rights.
The Brazilian government do not like how most Brazilians have become gamblers is what I see more to this but some gambling sites are still allowed in the country. I do not like to see money laundering and fraud to be referred to when talking about gambling sites. Bad money are in banks and owned by well respected people in the society. Most laundered money can not be linked to someone unless the source is traced to the person.
A popular proverb says "If you want to kill a dog, you start by giving it a bad name." We all know that most governments are corrupt and will always cover their shady dealing in conventional financial institutions. But they will also come up with reasons to go against other non-government institutions. We are not aware of the hidden reason why these restrictions have been put in place, but from what they have said, the move is worth it.