I think you're deceiving yourself with your implication that cheaters tend to be "extremely intelligent." Being able to exhibit intelligence in short bursts is not the same capability as being able to exercise it for hours a day, for months on end, in a mental marathon like academia or many other career paths require. The cheaters that you're referring to, are at best, clever, which is inferior to being intelligent.

You may believe that they simply lack the desire to use their intelligence over a longer timespan, but there is effectively no difference between never wanting to do it and not being able to do it.

There may occasionally be cheaters who cheat because they get a kick out of it, and happen to be intelligent, but that isn't the norm.