Why were east africans hostile to da gama when he first encountered them?

Vasco Da Gama was a famed Portuguese explorer who set out on expeditions in the late 15th century to find trade routes to India. He did so by traveling south around the southern tip of Africa, through eastern Africa, and across the Indian sea.

During his expeditions, he was met with hostility from East Africans. In Mozambique, Da Gama was met with hostility because he could not provide a proper gift the Arab ruler of the region. In the Kenyan region of Mombasa, Da Gama used piracy techniques to obtain goods on unarmed Arab ships. Later, the locals retaliated and Da Gama soon departed in April, 1498.