Julius Caesar, as Shakespeare presents him, is a powerful, charismatic leader, and brilliant military tactician, whose victories have inspired "the masses" with pride in Roman rule. He is able to compel loyalty, to a fanatic extent, in those under his command.
But, although Shakespeare is at pains to suggest ambiguity in this situation, we are led to believe that he may, in fact, aspire to become a dictator, a supreme ruler whose populist support does not reflect the ideals of the Roman republic. This is why Brutus and the other conspirators fear him and eventually assassinate him. Caesar's success in his military campaigns, which rely on his "top–down," absolute rule, leads him to believe that this system is also the best way to govern a country, or, in this case, an empire. He has not grasped the idea that "absolute power corrupts absolutely."