Final answer:
Hostility toward Vasco da Gama during his encounters in East Africa can be attributed to the Portuguese aggressive monopolistic tactics, the threat of European colonization, and cultural and religious differences, which included a history of Islamic trade ties that were being threatened.
Step-by-step explanation:
East Africans were likely hostile to Vasco da Gama and the Portuguese due to a combination of historical, religious, and strategic factors. First and foremost, the Portuguese approach to interactions was generally aggressive and often aimed at establishing a monopoly on the spice trade and imposing control over territory. This would have likely led to resistance from East African communities and traders who had their own established trade networks and alliances. For example, after failing to secure an exclusive agreement in Calicut, Vasco da Gama demanded that all Arabs be expelled, and when refused, he bombarded the city. This aggressive tactic was an affront to the existing economic and social systems in place.
Furthermore, the East Africans would have been aware of the European colonization efforts and the accompanying violence and exploitation that characterized their expansion. The Portuguese and other Europeans employed strategies such as divide-and-conquer, which involved allying with some local rulers at the expense of others, creating distrust and enmity among those targeted.
Finally, the cultural and religious differences likely played a role. With a history of Islamic trade and conversion, many East African societies had formed connections with Muslim traders and the Islamic world, which might have led to resistance against the Christian Portuguese newcomers. As Islam spread primarily through merchants, traders, and scholars, these regions had developed their own religious affiliations that were being threatened by the Portuguese presence.