Do people even understand what that means?
No, they don't. And they don't want to understand. Just look at how indifferent many are about what is happening on the other side of the planet. If offered an exclusive choice between a 50% reduction in gasoline prices and the complete cessation of all authoritarian and totalitarian regimes without prolonged wars and massive devastation, many would choose the first option. Instead of the cessation of authoritarian regimes, you can point to solving any other global issue like climate change - and they would still choose the first option. This utter indifference, mixed with all sorts of absurd destructive beliefs such as conspiracy theories or racial superiority, provides very fertile ground for the establishment of authoritarianism.
Finally, I see comment from someone who clearly understands this. Somehow, many people perceive such a threat very non-seriously, as if they think it will never happen, or that someone will come and prevent it from happening.