The year is 1780. The printing press is the pinnacle of technology, there's no such thing as an adding machine. Most correspondence is done on parchment with a quill pen. The majority of Americans cannot read or write. Information cannot travel beyond earshot faster than a galloping horse. Elect a president by popular vote. You have four months.
That's not even it. At the time the Constitution was adopted, there were states like Virginia that had a lot of people, but rather few voters. They were afraid that they wouldn't have a real say in who the president was. The Electoral College was a way to inflate slave states' power, and entice them to join the Union.