Comment by IAmBroom

It's not that they'll be able to call on one another - you can't guarantee who else will be around after The Bad Event (whatever it is).

It's that they don't have the basic strength of building alliances in the first place - something every kid is supposed to learn through the joys and pains of playing together. Bullies are not generally the popular ones, but neither are the loners.

To put it another way: castles can't survive siege forever. They are a delaying tactic until outside help can arrive.

"The Dauphin, whom of succors we entreated, Returns us that his powers are yet not ready To raise so great a siege. Therefore, great king, We yield our town and lives to thy soft mercy." -- Henry V, Act 3, scene 3