Civilisations and societies throughout history have been governed by the ruling class system. The English parliamentary system and the American revolution were isolated attempts at displacing the system of ruling elites.
I'd guess the impetus for this reform of the ancient central elite system was the expansion of the free market. The decentralised, unplanned free market system had been delivering improvements to the ordinary people for some time, without the participation of the central power elite, who if anything fought against the free market to protect their system of patronage. When people see their wealth coming from each other, and not a central authority, that central authority is on thin ice, especially when it comes to extorting taxes.
So, the ruling class were tamed by a system of contrary powers. Power divided is power diminished.
But the left is against limitations on the power of the elite, because they consider themselves rightful members of a ruling elite and resent limitations on their own powers. The left is a counter-revolutionary movement trying to undo the limitations on central authority brought in by, for example, the American revolution.
The left are a part of the push-back from the old system. At least that would be part of it. The other attraction of the central authority system is that it's fairly simple to understand: Central authority says do 'A'. People do 'A' (or else). It's simple enough for the adolescent mind of the leftist to grasp.
It's even worse when the left are the elite, because at least in the old system the ruling elite were either the strongest and smartest of their society, or at least employed the strongest and smartest. The modern left, by contrast, are a bunch of dodo heads.
