This seems like a fairly obvious yes since his performance is no longer hypothetical. Donald Trump is a mentally impaired bigot who combines inattention to detail, massive ego, inability to select quality underlings, and failure to manage and performed abominably.
None of them were competent enough to make an informed decision insofar as the leadership of the nation because they relied on faulty analysis, willful ignorance of Donald's many flaws, and self interest in lower taxes.
I'm not sure why this is controversial. The average college educated individual is presumably skilled in their profession but their profession but that is hardly sure to inform their understanding of matters out of scope of that profession.
Do you find it surprising that 30% of any group makes poor decisions?