The best answer would seem to be that it depends on which leader you are discussing, and which people in a given country you ask.
A friend who visited Argentina in the 1980s said that he met plenty of people who still openly worshipped Juan and Evita Peron. Old newsreels from Nazi Germany show women staring at Hitler in about the same way that some teenage girls reacted to The Beatles when they arrived in New York in 1964. A Filipina with whom I worked in the mid-70s was pretty well convinced that the difference between Ferdinand and Imelda Marcos and other people was that when they defecated it smelled really good.
On the other hand, I recall reading a memoir from a man who lived in China during the Cultural Revolution. One night he was awakened to participate in a “spontaneous” demonstration of support for Mao. While he jumped up and down in the street in mock excitement, he had no doubt that virtually everyone else there was faking their loyalty as well.
And I am betting that no one really liked Caligula by the time he ate his own baby.
Fear is a great motivator. In the country or even out of it.
In the 1970s, I knew an Iranian immigrant who insisted the Shah was the finest human being on the planet, who would get indignant if anyone even hinted otherwise. The day the Shah fell–the freaking morning of the fall!–his line became “Shah who?”
As for the question of what people living in a police state know about the crimes of their government, a safe answer may be that some people know plenty (after all, somebody has to commit the crimes), a great many people know something is going on, but know less than people outside of the country, and some people manage to know nothing, or are so good at denial that they convince themselves they know nothing.
It has been argued endlessly whether the German people were aware of the atrocities being committed within their country by their own government. The Nazis were extremely careful in suppressing information about this, even going so far as to avoid terms such as “executions” and “corpses” in official records in concentration camps. Some years ago there was a revisionist historian who even suggested that Hitler himself didn’t know about The Final Solution. I don’t buy that, but he actually was able to come up with documents with which to make a case, albeit an unconvincing one.
At the same time, well before the imprisonment of Jews, the Archbishop of Bavaria publicly accused the government of exterminating mental patients, arguing that the wereabouts of far too many of them were unaccounted for.
My WAG is that most of the time most of the people in a police state “sort of know” what is going on even if they are not aware of the scope and variety of the crimes which are being commtted. Totalitarian states remain in control via fear and force, and that can’t work unless people know that there is force they need to be afraid of.
There are, of course, always a substantial number of people who manage to know pretty much nothing about anything; one of the prospective jurors in the Oliver North prosecution said during voir dire that she didn’t know anything about North except that he had been the commander of our troops in Iran.