A nice theory I found

[Knight Theamion]

Forms of government change. Long ago James Burnham, following Hobbes, pointed out that while it is easy to convince people that government is valuable, it is not quite so obvious that any particular form of government is best. The belief that fifty percent plus one will best look out for the interests of the whole is as much a myth as the Divine Right of Kings, and certainly no more compelling than the notion that the state may be best placed in the hands of those educated to the task. Alexander Hamilton, himself "the bastard son of a Scots peddler," argued for a strong hereditary component to the United States Constitution on the grounds that an aristocracy would look to the future and not merely to the next election. Clearly he expected an open aristocracy which could be entered on merit, but he was not shy in defending hereditary rights for those who had won admission.

By the Twentieth Century it had been repeatedly proved that the qualifications required to obtain the office of chief of state were not optimum for actually performing the job; and this regardless of whether the state was a constitutional republic like the United States, or the kind of revolutionary anarchy favored by its southern neighbors.
If the ancients from Aristotle to Machiavelli were agreed on one thing, it was that when a state required strong armed forces for its survival, those armed forces had better be commanded by a single person; that the political crimes of one bad ruler were infinitely preferable to the dangers of dividing military command. Better Tiberius than a committee. The first two hundred years of the United States of America seemed to disprove that thesis, partly because prior to 1950 the United States would never have dreamed of keeping a large army in time of peace, and even had it done so, that army would have been conscripts, not long service volunteers.

The events of the Twenty First Century demonstrated that the ancients may have been wiser than the moderns thought . . .

[Tactitus]

Originally Posted by Knight Theamion

If the ancients from Aristotle to Machiavelli were agreed on one thing, it was that when a state required strong armed forces for its survival, those armed forces had better be commanded by a single person; that the political crimes of one bad ruler were infinitely preferable to the dangers of dividing military command. Better Tiberius than a committee.

I don't think the ancients were nearly as agreed on this 'one thing' as you suggest. The dual kings of Sparta and the dual consuls of the Roman Republic are but two examples of states opting not to go with a unified military command. Divided political (rather than military) leadership was even more common.

Not seeing your point, tbh.