It was popular in the fifties for two reasons.
1. The US has just finished fighting two wars at once, in which Americans put away their differences and united.
2. The Cold War was indeed existential. We lived under the threat of nuclear annihilation, which required that we unite in anti-communism. Which we did, fighting domestic communists.
We didn’t need to read the highly symbolic, ambiguous Revelations to get a clear picture. We lived unity provided by an outside threat.
Same alert to you, Don’t Take The Mark when it is commanded to you. Remember, you have been given an alert in advance. Remember