Ideas on Earth were badges of friendship or enmity. Their content did not matter. Friends agreed with friends, in order to express friendliness. Enemies disagreed with enemies, in order to express enmity.
The ideas Earthlings held didn't matter for hundreds of thousands of years, since they couldn't do much about them anyway. Ideas might as well be badges as anything.
They even had a saying about the futility of ideas: "If wishes were horses, beggars would ride."
And then Earthlings discovered tools. Suddenly agreeing with friends could not be a form of suicide or worse. But agreements went on, not for the sake of common sense or decency or self-preservation, but for friendliness.
Earthlings went on being friendly, when they should have been thinking instead. And even when they built computers to do some thinking for them, they designed them not so much for wisdom as for friendliness. So they were doomed. Homicidal beggars could ride.