I feel the original question was more in the line of "Why are US presidential election are not like elections in the many other democratic countries?" and is a huge trivialization of a complicated issue.
Forget or deny to know? For people living in the USA, forgetting that must be quite a challenge; every four years, there's half a year of real reality tv, extensively covered all over the news, to remind them of it.
It's not obvious by any means, that's why I pointed to the reference work on that topic. There are reasons the electoral college was implemented, whether they are still valid of not is a different question entirely.
Furthermore, it's not even clear what the question is. Why it's not elected by the US populous? Because it's the President of the United States being elected, not the President of the people of the United States. Why is it not a direct vote? In part, to make the system resilient to the tyranny of majority which was feared by Founding Fathers.
There is extensive literature on that topic by the designers of the system itself and one cannot summarize it in a HN comment. So if the the Americans the parent was referring to are indeed puzzled by that question there are answers to be found.
