How did rulers and dictators get so good at dominating people who don't like them?

I often wondered just how do dictators and rulers are allowed to rule? Be it they came to power by revolution, birth, a government or military coup how do they stay in power? It is usually one man and his cronies that run the show. Many of these rulers are doofuses and/or truly vile and ruthless. I am sure many working close under them in the regime or government despise them and maybe think in the back of their mind that they could just reach out and snap his/her neck or cut them down right there. I am sure the know others have to feel the same but is the fact they don’t know who or how they would react they say nothing? And could they have been working with others in the “inner circle” that thought just as they do but because of fear they work years or decades right under a monster not knowing they would have had support? How do these dictators get everyone running in fear that no one dare tell a sole they want regime change out loud that like-minded people could cobble together?