Humans are incapable of being rational, it's not how our brains function. We can, with great effort, emulate what we think rational thought would be like.
Human brains regularly lie to themselves because it is cheaper or easier than actually processing input.
You know that fun retort: "Who are you going to believe, me or your lying eyes?", and how it's always trotted out as this supposed retort to someone suggesting you ignore obvious info, but our eyes are lying to us constantly. There are tons of ways your eyes cheat, or lie, or outright ignore reality in favor of some internal model. This isn't even limited to optical illusions!
And the same is true of all sensory input we have. There are auditory illusions and ways your ears lie to you. There are things like phantom limbs that demonstrate your brain will ignore explicit and clear reality for no reason.
Humans are emotional creatures, like all biological creatures. Humans make choices emotionally
Do you think the most emotionally charged information will always be truthful?
The outcome we are experiencing was obvious, but people ignored it because that sort of implies that information needs to be filtered or curated and that makes people nervous.