The Electoral College resists “tyranny of the majority”, critical in a nation devoted to individual liberty.
The Framers' design was to secure the objectives set forth in the Preamble to the Constitution.
To this end, the purpose of the electoral college was to appoint a man of nationwide reputation unbeholden to factions or political parties.
Only then, when Presidents didn't owe political debts, could they be expected to fulfil their duty to "preserve, protect and defend the Constitution of the United States." The Framers would recoil at the idea of limiting the practical vote of state electors to one of two nominees of outright political factions.