Because our history has been white washed. Jeffrey Robinson of the ACLU has a great talk on it.. The Truth about the Confederacy. It is on YouTube.

It is and it isn’t. The House of Representatives being allocated based on the 3/5ths compromise is, and that is now how the number of electors are determined for each state. Number of senators plus number of representatives. But the electoral college was initially put in place because the only people who could vote were land owning white men, and they were pretty spread out. So they voted for electors who traveled to a central location and did the official vote. It was mainly logistics.