Except the-service-formerly-known-as-Twitter isn’t being “shut down”, it’s being stopped at the Brazilian border. This actually happens all the time with print publications in many countries that don’t take Free Speech to toxic extremes—they get confiscated at the border by Customs officials. It’s less common these days than it used to be, but I’d bet that there are still instances of fringe porn and unapologetic Nazi propaganda being seized.
X-Twitter is free to go about its business in the country in which it’s based and in any other country where it hasn’t been banned, just not in Brazil, until and unless it decides to comply with the courts there. Which it is free to do at any time.