Basically it shows how one family spent their money for the worst case scenario in building this shelter, their friends spent their money throwing lavish parties. They of course didn't even think of building shelters of their own. Only once when there was a threat the other families paniced and tried to get into the shelter. Once desperation sets in they tried to break into the doctor's shelter. They didn't even give a thought about how the doctor was trying to save his own family by paying for his own shelter while everyone else wasted their own money and now needed a safe haven of their own.
In the end with the disaster averted, the friends just tried to brush the incident off as if it were one big 'misunderstanding' even stating they would have yet another party to celebrate their survival. However, the doctor summed it nicely on how it showed people can be savages in order to get what they want and how their 'friendship' will never be the same again.
IMO rather than just picking new friends, I see it more as how selfishness is the downfall of people as if they don't plan for the future as then the figurative bottom will give out below them.