They are not that stupid, generally speaking. More like they are all lying for the sake of their selfish gene that demands that they be tribal and badly in need of fellowship.
I live in a country that calls itself "Catholic country". We even have written contracts with Vatican and are giving lots of money to Catholic Church (even though we are the poorest country in EU) and have Christian "indoctrination" in elementary school as one of the optional classes, and if your child doesn't attend he us looked very unfavourably upon by other parents. Christian cross is main ornament here, around the neck and in some visible place in the car. My mother tried to convince me to be a good boy and become a Christian since ages 10-20, with numerous priests coming into my house to talk with me. Every visit came to a very abrupt halt because I asked some "inconvenient" questions. Nothing special, mostly regular things, like "Why God/Elohim is referred in plural?", "Why would God be afraid of men and expel him from Eden?", "Why God didn't know where Adam was?", "If all is according to Gods plan, than why would Adam be condemned for doing what God has planned?", "If everything is already planned by God where is the free will?", "Why would God plan sins in Sodoma and Gomora and genocide that followed?"...and when I brought Churches wealth, power, inquisitions, crusades, only unchanged gospels that we know of (Nag Hammadi library)...it all went south for the priests and they left pretty fast. Usually saying "Jesus still hasn't revealed to you and I will pray for you.", but it was always said in a very defensive and prerogative way.
Why am I writing all this? Well, the selfish gene in me should have activated, as 95% of people in my country call themselves Chatolics, and with all added pressure by my family - why it did not is beyond me. I have some personality traits that are almost commanding me to tell the truth how I see it. I got in lots of trouble and was punished for it from an very early age. Both from my peer group, my family and schooling system. I have an IQ (had to have it measured because something was obviously "wrong with me" as I was not complying with my societies norm and was underperforming in school) that is "above" 98% percent of other people (above 130), but at the same time I will say or not obey if I think it is "immoral/not intelligent" to do what I am asked. I suffered personal loss because of that but I am not changing my modus operandi even now, when I am 40 years old. I just can't. If I would disrespect my moral code I would go insane pretty fast. I consider "Christ consciousness/ Buddha nature/ Krishna nature/ "choose your naming", exactly that - the "impuls" in us that is opposing selfish gene and is looking at the biggest picture possible, for oneself, family, humanity and life itself.
This is not the "song to my virtuosity", but an attempt to explain myself to myself. It is a mystery to me why am I almost compelled to think and act in this way when "going along" would bring much more outward peace and material prosperity to myself. I almost feel like a virus in a very corrupt, but well established program. I will stop now as I feel that I am glorifying myself. Maybe I'm just stupid and actually don't get the bigger picture. It is always "the great who knows" for me...
Peace.
Edit: I think I came out as holier than thou in my description and nothing could be further from the truth. I made and am making lots of mistakes. I occasionally do thing that are not in alignment with my moral code and do occasionally go insane. This is all based on how I perceive reality and morality and I allow that I am way off, crazy, even evil just don't see that. With that said I am clicking Save.