there are a few factors. there is the weighting ( how many electoral college votes per citizen) as well as how they get allocated. If California has a single voter more for Biden and Trump, it's the same as if nobody in California voted for Trump. If your state has 100 electoral votes and the voters are split 50-50, the fair thing to do would be to allocate those electoral votes 50-50. Instead it's all winner take all, making people further feel like their vote doesn't matter. The probability that your vote is the swing vote is so low compared to a simple popular vote for the vast vast majority of voters, so at least with regards to the presidency, they have a lot less reason to even vote.