If the MC were of a different race/origin or had political ideals that didn't go well with those of the alliances, or maybe the alliances didn't get along in the first place and the MC is just the hair that broke the camel's back. Maybe the alliance is using him as a scrape goat or setting him up because he's the new guy. Or it's really a diversion so no one will be paying attention to what they're doing on the sidelines.