Europe did the same and it worked.
Maybe they should make their government standard good enough that it wins on its own merit then. Imo, the biggest thing this block does is essentially giving the government standard a license be as subpar as they want, because it isn't like a superior non-government standard is even allowed to compete with it anyway.
Maybe when it becomes a champion on that, removing barriers of entry, protectionism, subsidies and it's public companies monopolies, then it can be a fair judge on this issue.
The Brazilian Central Bank has authority on money transfers, so whatever regulation they want to arbitrarily impose regarding this matter, they can do.
Facebook is a registered company in Brazil, they were going to operate the payments platform through a card processor, etc, so directly or indirectly they are under the authority of the Central Bank.
EDIT: by the way, regular banks and fintechs already have to be a participant in the Central Bank's payments system in order to settle funds. PIX is (also) a 24x7 implementation of the existing electronic money transfer system which only is available on working days.