What possible reason could there be for why more people did not live near the Niger river delta

For the roughly fifty years since Nigeria declared independence from British colonial rule, oil has been produced in Nigeria. Throughout this period, corporate politics has intersected with successive dictatorships. Under these dictatorships the Nigerian government has signed laws that appropriated oil resources and placed these under the control of multinational oil companies, such as Chevron Corporation and Royal Dutch Shell.

From the point of view of MEND, and its supporters, the people of the Niger Delta have suffered an unprecedented degradation of their environment due to unchecked pollution produced by the oil industry. As a result of this policy of dispossessing people from their lands in favor of foreign oil interests, within a single generation, many now have no ability to fish or farm. People living in the Niger Delta have found themselves in a situation where their government and the international oil companies own all the oil under their feet, the revenues of which are rarely seen by the people who are suffering from the consequences of oil extraction.

Kenneth Roth, Executive Director of Human Rights Watch, has said of the situation:

The oil companies can't pretend they don't know what's happening all around them. The Nigerian government obviously has the primary responsibility to stop human rights abuse. But the oil companies are directly benefiting from these crude attempts to suppress dissent, and that means they have a duty to try and stop it.

Explanation:

https://en.wikipedia.org/wiki/Movement_for_the_Emancipation_of_the_Niger_Delta