Neither the Founders nor the Framers of the U.S. Constitution dictated that a state's Electors should be appointed on the basis of state-wide "winner take all." Rather, how that was to be done was to be left to the discretion of each state's legislature:
"Each state shall appoint, in such manner as the Legislature thereof may direct, a number of electors, equal to the whole number of Senators and Representatives to which the State may be entitled in the Congress: but no Senator or Representative, or person holding an office of trust or profit under the United States, shall be appointed an elector."
U.S. Constitution, Article II, Section 1.
The winner-take-all approach didn't become the universally accepted method of "appointing" Electors until the election of 1836 (although, even then, South Carolina had gone its own way).
Which is to say, there is nothing constitutionally sacrosanct about the winner-take-all approach. Rather, it was something states eventually settled upon for various pragmatic political reasons.