King Anawrahta converted Bagan to Theravada Buddhism not only from genuine spiritual conviction but also to weaken the powerful and corrupt Ari Buddhist monks, bringing the church under royal control.
The podcast explains that King Anawrahta used the austere Theravada Buddhism brought from Sri Lanka as a tool to break the power of the Ari monks, who owned vast estates, practiced martial arts, and were said to demand first-night rights with brides.
transcript
Paul Cooper (narrator): Perhaps King Anawrahta was genuinely moved by the sage's teachings, but it's clear he also spotted an opportunity. If he brought this new branch of Buddhism to his kingdom, he could weaken the hold of the Ari monks. So, King Anawrahta went to war with the church.