The electoral college is to stop smaller states from being overwhelmed by bigger states. For instance, if it was just by popular vote politicians wouldn’t give a shit about smaller states like Vermont, or New Jersey. They could just visit the big states like Texas, Cali, Florida, etc, and the smaller states would be left in the dust. Keep in mind many states have different needs and laws that might be good in Cali could be detrimental to Washington. the ELI5 is the entire Constitution was the culmination of compromises. That included the electoral colleges that allowed the less populous states to have somewhat equal power with the more populous states.
Because the popular vote is quite literally an illusion. The only real purpose a system like this could have is in counting votes in a nation where the internet doesn’t exist. Instead of having 100 people count ten million votes, you can have those hundred people count 25,000 votes. It was necessary at one time. Literally the electoral college would have you believe that their math is more accurate than that of a computer. Have you seen some of these people?? Lol