There are many, many reasons to doubt the official version of the plot. Granted, the facts are difficult to establish. Accounts from that time are incomplete and often contradictory. Key documents are missing; others have clearly been altered.
But let's just focus on one detail: that mysterious letter to Lord Monteagle. Over the centuries there have been many people suggested as its author.
Did Monteagle write it himself, in order to curry favor with the King?
Was it an attempt by one of the conspirators, Monteagle's brother-in-law Sir Francis Tresham, to give him a veiled warning? That was co-conspirators Catesby and Winter's suspicion when they heard the next day that their secrecy had been compromised. They were going to kill Tresham until he convinced them that it was not he who had betrayed the plot.
Oddly enough, when the conspirators learned that the gunpowder had been discovered, they did not immediately abandon their plans and escape to Flanders across the Channel (Fawkes had a ship waiting to take volunteers to the English regiment that was fighting on the Spanish [Catholic] side against the [Protestant] Dutch.)2. Instead they persisted in their plans to rouse a Catholic uprising in the English Midlands once the king and his government were destroyed.3