Good afternoon.
This is a well known episode in Portugal how John VI moved to Brazil when French troops invaded, and even more so known around here in Reddit how he "moved" the capital of the Empire along with him.
He left a representative government behind to meet the french, but to the common population this seemed like a complete flight and abandonment of the country to its luck.
But in all reality what could have happened to king if he had stayed? Would he be deposed, forced into exile, executed or made a puppet? What happened in other countries in Europe that could be taken as an example?
A good example was what would happen a year later in Spain. There the Spanish King was forced to abdicate and held in captivity till 1814 and one of Napoleon's brothers was given the crown.
Certainly João had no reason to think that Napoleon was likely to treat him well. Portugal was a long ally of Britain. And by breaking with the continental system, he had angered Napoleon. And Napoleon was coming to make an example of João. Death wasn't likely. But he was almost certainly going to lose rulership.
And it is to be remembered at the time João was ruling as a Prince Regent for his insane mother. So he didn't have an ironclad claim to a legal right to rule as it was. There had been controversy when he became Regent. And there had been a competing plan for a Regency Council. There were also popular concerns that he was mentally unstable as well.
So the idea that he might disappear into a personal mental ward with a private doctor appointed by Napoleon wasn't out of the question. And if that were to happen... well he might never get out of that private sanatorium again. And Napoleon could appoint a Regency Council that Napoleon could control.
João had plenty to fear, for himself, his family, and his country.
And let's not forget that the British fleet that had arrived to whisk João to safety wasn't exactly altruistic either. If he didn't accept their offer, they had 7,000 men and orders to capture Lisbon and keep it out of French hands. His options were to run from the French, run from the British, or to barricade himself in Lisbon where he would certainly be eventually be captured by one or the other. I guess in the end Brazil sounded like the best option. And having lived there myself, I think he chose well.