I have this kinda schizo theory that the ancient Kitakamians had always wanted to get rid of Ogerpon and the Loyal Three fiasco simply gave them the perfect excuse to do so. The people of Kitakami have always been huge autists towards outsiders which is the reason they treated Ogerpon and the Paldean man like subhumans, only begrudgingly accepting them after they start hiding themselves behind some really cool masks. But then the masks become more and more popular to the point they're world famous and it's only a matter of time until people want to learn more, and "Oh yeah we wear these so we're allowed to commune with others, else we're ostracized from society and forced to live in a cave, haha it's okay though we have each other" is not what you'd call good PR for Kitakami. But before that happens Ogerpon bashes a bunch of Pokemon's heads in and that's all Kitakami needs to go full into confirmation bias. Let's not question why the Pokemon were in possession of three of the four masks or why the man mysteriously goes missing after this and even berate the mask maker for siding with the ogre because this proves outsiders are all evil and violent and cannot be trusted.
Of course there's the irony of worshipping a band of thieving outsiders in your effort to keep outsiders out which is the cherry on top
