^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
I've just been browsing thru 'Pocket Empires' & it mentions that as a result of Cleon's coup/usurpation/whatever the Zhunastu Corp now had an effective monopoly on any & all gov contracts & thus effectively began squeezing out all competitors.
Some of which actually (a scenario is included) went off into the hinterlands to try to duplicate his feat for themselves. It occurs to me there were probably any number of alternative methods to secure effective economic hegemony, some of which may have even been more efficient. However choosing a different tack wouldn't have allowed Cleon to don the imperial mantle of 'greatness' & achieve a sort of immortality... very ego-appealing, no?
This is another 'psychology' aspect, but you've hit it on the head: Narcissism, entitlement, and egocentric thinking. MANY people who aspire to, and are ruthless enough to rise to, power show degrees of this (I can think of one in the US now... he may or may not be appreciated for decisions or policies, but almost none could deny his own sense of his own importance).
I think once you are in charge of a lot of power, it becomes possible to imagine you could be in charge of more and be even greater and have a greater legacy. And perhaps that you are infallible and perhaps a good personified (I think a few Roman leaders were heading that way in their minds).
I think ego drives a lot of powerful people (mostly men) to make risky plays (say, invading Poland in 1939... or trying to join NATO while living next to the Russians.... many risky plans made with bad outcomes....). Psychologists have spent a lot of time studying stock day traders which is an ego-driven, risk-rich environment where there is a sense of 'having it' and being able to win in the markets. Often enough, that ends up in a bad place eventually. I think politics works much like that the further you get into small oligarchy or charismatic dictator territory. Democracies avoid this simply by being chaotic enough and difficult enough to get on the same page to make that a rarer outlet.