While they benefited from it later at this point Virginia was a population powerhouse, the actual states pushing for this were the small New England states, I think some of them only gave up their giant western claims(google 'long connecticut') in exchange for it.
It was also a compromise. Proto-Federalists wanted a direct democracy determined by population, Proto-Democratic-Republicans wanted each state to get one vote. In the end they split the difference, House was determined by population, Senate by states, and the president by a hybrid system that didn't fully give either what they wanted.
If you went back in time to stop the electoral college you could just as easily get a 'One vote per state for president, 26 votes wins' system instead of a direct democracy.