Our forefathers thought that regular people alone weren't good enough to choose the leader of their country.
From Federalist No 58 by Hamilton
Another reason for the system was that Southern states had a smaller voting population because of slavery. Since slaves were counted in the census and went toward the number of representatives, it gave Southern states a stronger voice.
From Federalist No 58 by Hamilton
It was also peculiarly desirable to afford as little opportunity as possible to tumult and disorder. This evil was not least to be dreaded in the election of a magistrate, who was to have so important an agency in the administration of the government as the President of the United States. But the precautions which have been so happily concerted in the system under consideration, promise an effectual security against this mischief. The choice of SEVERAL, to form an intermediate body of electors, will be much less apt to convulse the community with any extraordinary or violent movements, than the choice of ONE who was himself to be the final object of the public wishes. And as the electors, chosen in each State, are to assemble and vote in the State in which they are chosen, this detached and divided situation will expose them much less to heats and ferments, which might be communicated from them to the people, than if they were all to be convened at one time, in one place.
Another reason for the system was that Southern states had a smaller voting population because of slavery. Since slaves were counted in the census and went toward the number of representatives, it gave Southern states a stronger voice.