Why was Portugal unable to establish a long term presence in the region?

Answer 1

There were several reasons for the fall of the Portuguese. First of all, as a small country, they lacked the resources to rule such a large territory. Their choices of administrators were poor, and there was much corruption as a result. The Portuguese and the Africans didn't relate to each other well. The Portuguese ruled n such a brutal manner that they became hated and despised.

Answer 2

Portugal as a small country in association with the Spanish in the 17th !8th century found themselves on the wrong side of a dispute with the English, the Dutch and even the French. The first two powerful maritime and imperial powers. In time the Portuguese were obliged to cede power principally to the English and the Dutch. Portugal still managed to hang on to Macao until the Twentieth century similarly its possessions in Africa, principally Mozambique.