Why would the introduction of Christianity to the Igbo people create conflict?

Because it is challenging their current beliefs that probably date back more than a couple hundred years

Igbo, also called Ibo, people who live mainly in southeastern Nigeria, and speak that language.

Religious conflicts are often caused by the use of religion to promote independent non-African churches, and Christianity provoked that conflict in the Igbo people.

On the one hand, there was the Muslim north, prepared under the English indirect rule, which accommodated the sharia legal system; On the other hand, there was the Christian / animist south, guided by the British-secular regime.