Read Luttwak's book, now I can give direct examples to some of what he discusses. However he builds upon the premises of a small coupist force infiltrating the capital city (replace the legal capital with Rio in this case) none of which apply here, though Mourão Filho's original concept >>39547 is as close as it gets.
It is completely unnecessary to take over the capital when the following take place:
-A sufficient threat of bloodshed is offered by the incorporated forces (4th Infantry Division, IInd Army), even if they're weaker than legalist reaction forces
-The government is afraid of bloodshed
-The government is led to panic and retreat after seeing defections, particularly a defection of a powerful, geographically close commander deemed trustworthy (i.e. Kruel)
-A foreign power threatens to recognize a parallel government
There was no classical storming and takeover of Rio de Janeiro. Rather, the government was bullied from outside into leaving it and the empty edifice of power was taken over. That's definitively a different kind of coup d'état. It probably still fits the definition.

On the other hand the 1961 coup was more of a pronunciamento, not an armed takeover but a veto by the military leadership to the Vice President taking office; it turned into troop deployments when the IIIrd Army refused to follow suit. Another pronunciamento could be the Colonels' Manifesto of 1954, a mere declaration which made President Vargas fire minister Goulart.
What still puzzles me is the difference between 1961 and 1964, how one failed and the other succeeded. There was mass political engagement, it was an age of populism - "a significant part of the population takes an active interest in political life—and regularly participates in it." On the other hand a significant part didn't.

In 1961 public opinion was overwhelmingly against the military ministers and they failed. In 1964 it was divided and the coupists won. In both cases there was also a degree of disillusionment with traditional politicians but that didn't stop enthusiasm for Goulart, which was one of them; I'm not counting this as a factor.
But according to Luttwak the overwhelming reaction against a coup by those engaged in politics, even if opposed to the government, should've taken place in both cases, but it only seems to have taken place in one of them. Public opinion wasn't supposed to have divided. So either there are more nuances to what determines it or it was weak/a nonfactor. After all in 1961 it wasn't public opinion alone but governors and the IIIrd Army, and even then their victory was hollow as the compromise of parliamentary government emptied the President's powers.