Prior to the shipwreck, Crusoe names the Portuguese captain as his heir. Why does Crusoe's plantation not go to the Portuguese captain when Crusoe is lost at sea?

Crusoe's disappearance was defined a civil death. The plantation was well kept by the Captain until the government claimed administration of the estate.

First, there was the account-current of the produce of my farm or plantation, from the year when their fathers had balanced with my old Portugal captain, being for six years; the balance appeared to be one thousand one hundred and seventy-four moidores in my favour.

Secondly, there was the account of four years more, while they kept the effects in their hands, before the government claimed the administration, as being the effects of a person not to be found, which they called civil death; and the balance of this, the value of the plantation increasing, amounted to nineteen thousand four hundred and forty-six crusadoes, being about three thousand two hundred and forty moidores.