The Portuguese court of the Barganza's- Maria I and her regent son the future Joao VI- relocated to Brazil (1808) and ran the empire from Rio de Janeiro after Napoleon's invasion. The court remained there until 1821. (Maria had been suffering from mental illness for years, I believe she was declared insane in 1792 by the same doctor who treated George III, and her son began using the title of Prince Regent in 1799).

During the Napoleonic Wars while the court was in Rio, Portugal found itself as a Protectorate of Britain and a virtual colony of Brazil. The Court was represented in Portugal by the British regency which was headed by William Beresford but acted in concert with Dom Joao. During this time British economic policies such as guaranteeing favored status to British products in Portugal deepened the economic crisis and created an anti-British feeling throughout the country.

Meanwhile in Brazil the transfer of the court brought great benefits to Brazil. To solidify their position the court granted titles of nobility to a few of the people that fled (or were forced to flee) with the court to Brazil in addition a minor minor amount of noble titles were granted to Brazilians. Additionally now that Brazil was no longer on the periphery of the Empire but its center its economy boomed. While slavery was illegal in Portugal it was perfectly legal in Brazil and with the economic boom Brazil's slave population increased dramatically. Also with the court in Rio, Dom Joao began a period of infrastructure building. In Rio, public libraries, gardens, sewers and operas were constructed. Roads were built to connect the major ports and cities of Brazil such as Sao Paolo & Pernambuco which were disconnected by vast tracts of rainforest. The first bank of Brazil was created, as were newspapers and publishers (which were heavily regulated) two medical schools and military academies were founded as well. Overall, the Portuguese court brought numerous improvements to Brazil.

With Brazil's newly found economic and political influence Brazilian nationalists and courtiers wanted Brazil elevated from its colony status to that of equal standing with Portugal. And once Napoleon was defeated officials back in Portugal wanted the court to return. But Dom Joao liked Rio (who can blame him?) so much he wanted to stay. While the beaches and weather were nicer in Brazil so was the political autonomy and popularity of the monarchy which were the real motivating factors. The monarchy was much more popular in Brazil and it enjoyed more freedom there. In December 1815 Dom Joao (as the Prince Regent) created the United Kingdom of Portugal Brazil and Algarves, thus elevating Brazil to a kingdom on equal footing with Portugal. Brazil having equal political and economic standing was now able to trade with other European nations freely, as opposed to when it was just a colony it was only able to exclusively trade with Portugal.

Back in Portugal after Napoleon was defeated in 1815 a group called the Supreme Regenerative Council of Portugal and the Algarve was founded and made up of Portuguese army officers, merchants and freemasons to end British control of Portugal and return the court. Ultimately this group was denounced and the British regency arrested many of them but found 12 of guilty of treason and sentenced them to death. Beresford ultimately was going to suspend the sentence but Joao VI, now king, confirmed it. After these men were hanged in 1817 this sparked protests across the country and deepened the anti-British feelings. As the situation worsened Beresford went to Brazil to obtain further support and resources from the King Joao VI. However, during his absence the Revolution of 1820 began in Porto, inspired in party by the revolution in Spain, and spread eventually to Lisbon. By the time Beresford returned to Lisbon with his newly confirmed powers from Joao VI the revolutionary officials back in Lisbon now had full control and denied him entry into the country.

These revolutionaries formed a temporary government and constitutional convention. They wanted the court to return, Brazil to resume its colonial status, a constitutional monarchy in addition to a more liberal government. A constitutional convention was held in 1821 and demanded that Joao VI return. He did so in July of that year leaving his son Prince Pedro in charge of the Kingdom of Brazil. On his arrival Joao VI communicated to the Cortes (the legislature) that he established a Regency in Brazil headed by his son and the crown would pass to his son even if Brazil gained its independence. The Cortes communicated back that they did not recognize his authority to designate regents, nor did they support the passing of the crown to his son in the event of Brazil's independence. In September of 1821 the Cortes abolished the Kingdom of Brazil, sent troops to Brazil to reassert authority and demanded Pedro's return to Portugal. Pedro refused to return and set up a new government in Brazil. This essentially escalated Brazil's independence as Brazil had virtually no representation in the Portuguese Cortes and Brazilian nationalists argued that Brazil's future should be decided by Brazilians and not by Lisbon. Im not going to get too much into the details of the Brazilian independence movement but ultimately Prince Pedro in Sept of 1822 declared Brazilian independence which was ratified in a treaty 3 years later with Portugal.

So Portugal did relocate to its colony. Not because of some arrogance but out of survival and necessity. However, with the Portuguese Empire now being governed out of Rio this only hastened the empire's dissolution (although Portugal did maintain other colonies after Brazilian independence) it did not prolong it.