How was the timeline botched? It started with the last summit, on the 28th of March, between the big 3: Mourão Filho, military chief of the revolution, and the 2 based in Belo Horizonte, his subordinate Guedes and the civilian chief, Magalhães Pinto. It'd been decided that the governor would write a manifesto, hand a copy to him and then at his green light it could be broadcast. No manifesto was brought. Mourão Filho wanted to enact his plan that very night as the meeting itself was eyebrow-raising, but couldn't without a manifesto. Then for the following days he waits and waits for it but the governor makes no contact.
According to himself he was willing to start at any moment and just waited. Other sources clash and state that after failing to start on the 28th he now wanted time to prepare. There's also the fact Guedes was superstitious and wanted an earlier date because of the Moon phases. And allegedly it was Marshal Odílio Denys, veteran conspirator present as a guest, who gave out the proper date (31st), knowing in advance Goulart's speech at night on the 30th would be explosive. Denys isn't very trustworthy.

The conspirators tripped on themselves on the 30th. In the afternoon Magalhães made a manifesto in solidarity to the navy, in light of the sailors' mutiny, and Guedes told his officers he was in rebellion. Both were meaningless. The governor's manifesto was only some vague words about democracy, allegedly it reached the President and he agreed with it! And Guedes' "rebellion" wasn't even known to the commander of the regiment stationed in Belo Horizonte (12th); he was in Juiz de Fora. Mourão Filho was only informed by telephone, when these events were a fait accompli.
By doing this the two won the political laurels of kickstarting the revolution and handed the hot potato to Mourão Filho who'd have to do the actual military work. Further, by writing a weak manifesto the governor even had an "exit strategy".
Yet it also compromised everything. By broadcasting their intentions before military preparations were made, they'd lose the element of surprise and have to mobilize under hostile conditions. If simultaneously telephone contact failed -that did happen with 60s communications- and the federal government took the rebellion seriously, then in the blink of an eye the Armored Division would be in Juiz de Fora while paratroopers fell on Belo Horizonte. And what if, on a whim, Mourão Filho chose to side with the government? With the Ist Army's support he'd march and crush Guedes & Magalhães.

However the federal government's intelligence failure and the weakness of the proclamations of rebellion meant nothing real happened. It was just enough to enrage Mourão Filho, who, after still waiting for a copy, by dinner made the fateful decision to act. He'd use a manifesto of his own.
He didn't want to watch the President at night as he'd commence his overthrow for before daybreak. His wife convinced him to watch because he'd overthrow him.
After that at dawn the governor's emissaries came with the manifesto. It was as bad as he expected and such was his rage they left in a few minutes.
At 04-05:00 he has the police occupy the telephone station and still wearing his pajamas and red silk robe sent a number of calls through the country, setting the coup d'état in motion. This is considered its beginning.