There’s enough evidence for me that it was intentional, Lucas is fascinated by the fall of Rome and what happens to societies preceding their collapse.
There’s some quote by Lucas comparing the fall of the Republic to the fall of the Roman Republic (comparing Palpatine to Caesar), and he comments that dictators don’t come to power at the head of a conquering army, but by turning institutions in on themselves.
So this guy’s fascinated enough by the fall of the Roman Republic to base a trilogy off of it, but not enough to know that Caesar actually did come at the head of a conquering army? The Senate gave him dictatorial powers after he conquered Rome, and it was an attempt to limit his power, not to give him power.
Palpatine also seized power through a coup via order 66, and with an army he created. I’m not sure I see the contradiction.
The quote you refer to also still points in the direction of Lucas’ intentions.