One of the reasons is that the language system in the Philippines itself is very chaotic. Before being colonized by Spain, the Philippines did not have a unified official language. The confusion of this language system makes everyone in the Philippines speak their own words, and there is no intersection between regions.
Another reason is that Spain did it on purpose. Because during the Spanish colonial rule, Spanish has always existed as an aristocratic language in the Philippines. Spanish can only be mastered and learned by a few Filipino aristocrats and upper-class people.
In order to keep the Philippines in the colonial state of Spain for a long time, the Spanish deliberately refused to let Filipinos receive education. Therefore, Filipinos have no chance to contact and learn Spanish because of lack of education.
In addition, another reason is also very important, that is, during the American colonial rule, English education was vigorously promoted. After the end of Spanish colonial rule, the United States began to colonize the Philippines. American colonial rule in the Philippines was mainly based on the promotion of English.
Therefore, Filipino became English in a short time. English has also become the main language of Filipinos besides their mother tongue. In contrast, although Spanish has a long history in the Philippines, it has not become the main language of Filipinos because of its small population.