Something wrong with the IQ test they used. Many countries below 80 and some in the 40s. I think this is culturely biased. The national average for most of the countries are standardise to around 100.

I can give you a few reasons:
1) IQ test the site used doesn't measure intelligence. See my previous post above. So if the test is wrong then the results can't be accurate.
2)we don't know how the site sample the population.

Having said that, a sample with higher rate and quality of education will likely to have a higher IQ. But not to the extent that the site pointed out.