“Why do people believe it will be different when they take over?”
I don’t. I subscribe to the notion that man in his or her normal state is fallen, venal, self-centered, power-hungry, and evil until they are changed through the grace of God. Since Leftists have purged God from their acceptable sphere of influence, they remain as above. And “public service” does nothing to moderate their natural tendencies other than to empower them to realize their designs. Man is fallible and groups of men and women are just as fallible, if not more so.
You got that right.