The electoral college was necessary because it would have been logistically impossible for people living in 18th and 19th century America to be able to participate in a single-day one person one vote election, given their level of technology at the time.
That had nothing to do with it. It would have been extremely easy for people in each state to count the votes for that state, then bring those vote totals to the capital where those state-totals are added together to get the final country-wide count. The problem is that that kind of simple, one-person one-vote system means that each vote would be weighted equally, and in some states there was a large portion of the population that couldn’t vote but the state’s decision-makers still wanted that portion to affect how much say that state had in choosing the President.
So basically, the Electoral College is there because of slavery.