I can agree that it isn't 100% accurate to say  "the more stupid you are the more likely you are to believe in god." but I would argue that your chart supports the statement "That's why people with higher IQ tend to believe less in gods.". The hockey stick red line past 100 IQ (the avg IQ) is not easy to miss.

I have a problem with the chart though. Sub 70 IQ is considered dull.  Statistically, above 130 and below 70 have the same % of people (and are a statistically insignificant number of people, less than 5% total).  Why did they leave out the above 130 IQ but leave in sub 70 group, why did they only include part of the "bell"?  I surmise that they needed a big dropping red line somewhere to combat the lower intelligence = more theistic argument and found one the only place they could, in dullards...

To be fair present the proper distribution and remove the sub 72 on that chart and see what it looks like again.  This is so typical of an agenda driven presentation.  lol at using less than 2.5% population to argue anything about what is typical (read average).

It is crystal clear and supported by even your supplied skewed agenda driven chart that "people with higher IQ tend to believe less in gods."

Edit:  I read the chart like this.  As you go from dull to average (70-100) or in other words everyone below average intelligence you are more likely to be theistic.  As you go from average to genius (100-130)  or in other words above average intelligence tend to be less theistic.