Well thank god we have the MC to make these citizens' decision for them, with zero forewarning that their way of life is about to be uprooted and they just have to deal with it. If the dungeon really has to be dealt with, there are 1000 better ways to deal with it than a spur-of-the-moment unplanned dungeon destruction spurred from a spat over profits.
Again, the whole outbreaks thing is an after-the-fact justification that didn't play into any of the decision-making on the MC crew's part. It doesn't make their initial decision, made entirely without that knowledge, any better.