I think a lot of politicians are elected because they Do something. It might not be the right thing to do or the right thing might not be to do ANYTHING…this Dunning-Kruger Effect fits in well with that: “Git 'er done!!” or “Kill 'em all and let God sort 'em out!!”. It’s the whole idea that if you just grab the bull by the horns you can make something work out the way it should be.
Perhaps the smarter move would have closed the bull’s gate; no need to grab anything then.
I think a competent leader (foreman, managers, whatever) surrounds themself with intelligent people, those that may not be able to make a decision themselves but have good information. This enables the leader to take action when necessary because he has no trouble acting when he wants to.
This Effect may also therefore explain the Peter Principle (in a hierarchy every employee tends to rise to his level of incompetence).