I understand that the electoral college system was put in place to "protect" the southern states, whose slaves could not vote. In debating whether to have a direct national election, they pointed out that the north would always win because they had so many voters. But that only explains the formula for the number of electoral votes each state gets; it doesn't explain why the states don't get to directly say who those votes are cast for, but rather appoint actual people as electors who will meet to cast their votes.
Originally, in the late 18th century, a couple of reasons for this that I've read about were:
They didn't envision a party system, they envisioned the electors would be educated informed people who could select a good president based on their own judgement.
Communications across large distances were slow, so people wouldn't really know who they were voting for directly.
However, by the early 19th century when the 12th Amendment was passed, effectively tinkering with the electoral college system, both of those reasons were weak. By then, there were political parties, and people were generally voting for their party's electors, who would be expected to vote for their party's nominee for president.
So why, at the time the 12th Amendment was passed, did they keep the mechanism of having human electors, rather than say that each state gets to decide directly which candidate for president and vice president that state's votes would go for? What was the role of the human electors supposed to be, at that point?
Hi, hopefully someone can drop by to address your specific questions, but fyi there have been several discussions about the electoral college recently; this one is a good starting point
In debating whether to have a direct national election, they pointed out that the north would always win because they had so many voters.
This is actually an incorrect assumption that is gaining ground because of a Vox Article. In this thread questioning the meaning of the Vox article I explain that this assumption is unlikely to be true because the South would have had an extreme advantage either way (whether it was a popular vote or electoral vote) because states like Virginia had way more property owning white males than any other state. (I also point out that it's in contradiction to what the leading historians have said over the last 15 years).
People forget that by 1787, almost every state in America had slavery, with the exception of three or four, so the North still benefited from the 3/5ths compromise and the extra population for the electoral vote -- but just not as dramatically as most of the southern states since they did, indeed, have more slaves than in the north.
To answer your specific question: Why do we have electors: I actually discuss this in detail on my personal blog and also spoke about it on /r/AskHistorians here. Because I spoke about it in detail there, I don't think I should make another long entry which essentially would say the same thing. I will however try and clarify the answer briefly so that it directly answers your question.
The purpose of electoral college was to prevent the masses from having a direct say in the government. The masses elected state legislatures, then state legislatures appointed the electors. The reason they decided on electors was because many founders worried that having members of the legislatures (whether state or national) being direct voters would prohibit them from voting without bias (Federalist lawmakers are pretty much bound to always vote federalist since they need to strike deals and work with other members of their party). By forbidding electors from being a part of the national government, only private citizens could vote, who, theoretically were more open to voting for the "best" candidate.
Please let me know if you have any follow up questions or would like anything clarified.