Stalin doesn't fit the model of a simple tyrant in my view. For one thing, he ruled over a vast continental empire not a small city state. A city state that you can traverse on horse back within a day can be controlled without requiring a sophisticated administration.
A continent spanning empire on the other hand can only controlled if you have an administrative organization of at least 100,000s of people loyal to you. Stalin was the ruler of a huge sophisticated society and he governed out very successfully, engaging sweeping social and economic reforms, defending the country against an all out invasion by the until then most formidable army the modern world had seen, and turning a poor backwards country into a nuclear armed superpower that could look eye to eye with the world's richest, most advanced and most powerful other hegemon.
You don't achieve all of that by just imposing your will arbitrarily on people. You need a gigantic administration, you need scientists and engineers, loyal officers, and you need ideals to which intelligent people can swear undying loyalty without feeling like they are just bowing to a tyrant who holds a gun to their head. Stalin could only impose an arbitrary will on people within very narrow limits. He had a role to play if he wanted to stay at the helm and not be deposed, murdered, sent into involuntary retirement, or be done away with in some other way by the people around him. Those people are for the most part only loyal to him as long as there was no too obvious conflict with their loyalty to the country and the socialist ideals.
Compare that to the cliques that surround a conventional tyrant and are loyal to the tyrant for more immediate reasons - because his rule guarantees their survival, as they have made everyone outside the system their enemy. Tyrants like to surround themselves with foreigners and low, despicable people for that reason - those guys have strong reasons to be loyal to him, everyone else hates them. Read Machiavelli for some ideas.
Now with Stalin on the other hand, when he died, was there a huge massacre of his loyalists? Was there a purge of the administration by his successors? No, only Beria was murdered. Khrushchev only dared to openly condemn Stalin's methods years after Stalin was dead. That gives you a hint on how strongly Stalin had relied on people's loyalty to the country and to socialism instead of just to his person.