Hysteria and mob psychology. One person starts the panicked flight from reality, the rest go into “follow the herd” mentality.
Act in haste, repent at leisure.
Twenty years, fifty years, someone will ask, how could they be so stupid?
Read True Believer (1951) by Eric Hoffer. All of this laid out in simple detail on mass movements, push the herd, mob theater, etc. Great book and easily read over a weekend. Eisenhower had all of his staff read the book.