It's only because we overestimate intelligence we think of that, probably as part of the "Great Man" fallacy.
Science is not advanced merely by people with "amplified intelligence" -- it's advanced through thousands of scientists working independently and in co-operation and tons of hard "manual" work of testing, verification, experimentation etc.
Not just some sage coming in with his insights, a la Newton and Einstein (though that did happen with more frequence in the previous centuries when more "low hanging fruit" discoveries were available).
As for politics, it's usually "sociopaths" and/or good manipulators and liars that go far ahead, not people with high IQ specifically -- and those traits are even conflicting sometimes (e.g. people with high IQ but Aspergers).