The man in charge has said in the past that he admired dictators. Many did not pay attention to this.
Congress is easy to takeover by a political party and this happens cyclically, so no one was surprised by that.
People also ignored gerrymandering because both major political parties do that, and historically it can be undone.
However, the takeover and stacking of the judicial branch with political cronies was another definite warning sign. People that were paying attention noticed this came first, because it’s the brakes that can slow an administration from getting out of control. The brake lines were effectively cut.
If you’ve studied German history and World War II, you know that Hitler didn’t just happen. There was an imperialist history. Though not typically stated in this way, the U.S. has historically been an empire for much of the 20th century, if you consider bases around the world and involvement in world conflicts (and the same could be said about some other countries, NATO, UN, etc.)
The American people cannot rise up against its own government in any substantial way when (1) families are split with half of the people are brainwashed, and (2) they think that things can be undone after N years by voting that party out (but the opposing party can not pivot to undo the economic and world political damage done by the current administration).
Most dictators were not known from the beginning of their reign as evil incarnate.
Americans keep hoping to see in the news that someone will stop this, but they suspect that if they were to try to stop it, they and their families would eventually be punished or killed. So, they’re all just waiting a few years hoping that it will be undone, and that surely the military will not let the U.S. takeover a country that does not have a despotic leader; that would break the longstanding U.S. trend of only getting very involved publically at least if they are taking the stance of the respected jock defending the little kid getting beat up.