I don't necessarily think of atheists as smarter people
Please note my use of "necessarily". I am aware that smarter people often tend to be atheists. Also, please note that I am not trying to bash atheists.
Honestly, if someone tells me they are an atheist, I will not think of them as smarter or dumber than what they were originally. Until they prove to me they are smart in other ways, I will not make a judgement on their intelligence.
I know atheists may not believe in crazy superstitions or fairy tales, but to me, that doesn't necessarily make them automatically smarter than those that do. While the atheist community tends to criticize the religious community from spewing uneducated and ridiculous crap, I have seen a huge amount of emotional and illogical drivel from atheists, and a whole lot of them who are as rigid and stubborn in their unscientific beliefs as many young earth creationists are. Okay, atheists may accept evolution more than religious people, but that doesn't preclude that an atheist can be a moron in different ways. I'm studying science right now, and I can tell you I have seen loads of atheists spew utter nonsense and unscientific bullcrap and misinterpret and even fabricate statistics just like how some butthurt religious people do. Yes, I know not all atheists are like I described, and while atheists ON AVERAGE may be smarter than religious people, that doesn't excuse the fact that many outliers exist. I actually have a Muslim friend who was one of the top students in my high school and even in international competitions, routinely scoring perfect or near perfect on every test, outperforming even most atheists in my school. I'm not really religious, but it actually blows me away how intelligent he is.
Okay, its true that the smartest people tend to be atheists. The studies have shown that on average, atheists tend to have higher IQs. That doesn't necessarily mean that being an atheist makes your IQ jump. I mean studies have shown that American society is actually one of the most racially tolerant societies in the world, but that doesn't stop groups like the KKK and Stormfront from existing. In that light, I don't automatically think that being an atheist makes one immune from being a moron, anymore than being an American makes someone immune from being a racist. I'd consider a person who is an expert in geology, biology, chemistry, physics and geography but believes that a magical walrus started the Big Bang by peeing on a koala a whole lot smarter than an atheist who failed kindergarten, though obviously I would think VERY lowly of the former's belief.
tl;dr: While it is true that intelligent people tend to be non-religious and often atheist, I do not think that being an atheist automatically makes you a smart person. One may not have a delusion, but that doesn't mean that you can't be a moron in other ways.
Is it normal to hold this belief?
P.S. Again, I would like to point out that I am not trying to bash atheists, nor am I saying that all or even the majority of atheists think that being atheist automatically makes them smart. I am also not trying to bash religious people either, nor am I trying to defend the beliefs of the religious (I mean I was really tempted to throw a brick at the screen when I was dragged into watching "God's Not Dead"). I am simply saying that I do not think being an atheist automatically makes one smart, and asking whether or not it's normal to hold this belief.