So, the premise is there's all these nigh-unstoppable dragons that will break free of whatever is sealing them periodically/eventually, and Blue Moon figures the only way to beat them is through death/soul harvesting? or that the only thing strong enough once charged up is such an AoE that it'll destroy nations or continents when unleashed (destruction size required depends on the dragon)? Or yuuji but they don't know that.
Well, that's somewhat more relatable/understandable than a random death cult that wants to kill everyone including themselves. Though obviously attracts people who just want to kill people.