The world was a different place back then. Back then, your parents, your church, your local friends, the mainstream media were basically all your sources of truth for local events. If you had any contacts that countered the main narrative and ideology of the US, they might have been silent out of fear or perceived as cranks.
Now we’re in a post-truth era. If 911 happened in 2020, we’d still invade the middle east soon after. Our naked emperors would just be a lot more shameless about it.