How do catastrophes, natural disasters, and other major shifts, such as climate change, that affect human movement, thinking, and survival change planning, building, and the administering of collective necessity and the commonweal. Human civ’s spread is a part of this contextual question. Why did villages grow? Why would domestication happen?
Ease.
Yes, ease is a big part of it. I would add that mankind found early on that there was safety in numbers (though this has come to mean something entirely different in today’s society). Interdependency allowed specialization and responsibility could then be shared.
These days, major catastrophic changes in particular bring families, neighborhoods, a country together, however briefly before resuming their more individual lifestyles in a reformatted manner to adapt to the situation.