The whole thing with twitter being blocked is that it all stems from twitter, and especially Elon, being asked to deal with misinformation from right-wing groups. Including ones within Brazil.
Elon refused, threw a tantrum and shut down twitter's brazilian headquarters.
That had the domino effect of twitter being blocked because, from what i know, companies cannot operate in Brazil without legal representation. Their office in brazil being shut down means they dont have that there.
TL;DR Twitter is blocked in Brazil because Elon would rather lose the sites 4th largest user base, by country, than shut down right-wing propaganda and lies