Earlier quoted context omitted.
I was also told the following rationale: If elections are decided entirely by popular vote, then candidates are incentivized to campaign in population centers, and have no incentive to ever visit sparsely populated states. (Like, bringing your margin from 70% to 85% of 4 million people is worth more than going from 0% to 100% of 400k people.)
That only makes sense if you believe that land area is the appropriate unit to attempt to equalize political influence over, rather than people. If you think the people are who should have political influence in a democracy, rather than units of land, then it should be desirable that politicians campaign to as many people as they reasonably can.
Also, I guess it's the fact of "winner takes all within a state" that disincentivizes candidates from simply drumming up more support within states they've already won, more so than the distribution of votes per state.