This article is a nice practice in the actual science of politics, but it’s not rooted in reality.
1.) States determine their own rules. Voters elect electors per the Constitution. State parties make the rules on how the electors vote. Most rules mandate a pledge to vote for the candidate who wins the state. They can be replaced right up to the date when those electoral votes are cast.
2.) The President-elect chose to not campaign in California, New York, New Jersey and other states where he knew he didn’t have a chance. If he did campaign in those states, it would have definitely drove more of his supporters to the polls and would have likely driven his total vote tally up. Albeit, not enough to win the popular vote, but enough to probably keep the final tally within 1M.
3.) As the Trump and Clinton campaigns followed the electoral guidelines to win the election, it would be unlikely that the rules would be changed (the proportional vote argument you suggest is moot). If it were to be allocated proportionally, refer back to bullet point #2 as the likely scenario as to what would have happened.
As traumatizing as this election may be to some people trying to create scenarios of hope, the bottom line is that the sooner they come to terms with the results, the sooner they will be able to prepare policy to oppose Trump.