Most states are winner take all.
“it could virtually invite Republican-controlled legislatures to rewrite centuries-old laws ensuring that the candidate who gets the most votes in a state gets its electoral votes”
What the article is saying is that state legislatures could end the winner takes all electors and move to split electors by vote proportion like Nebraska and Maine do.
This would make it significantly harder for Dems to cheat to win since they currently cheat in deep blue cities to outvote the red rural and suburban areas.
State legislatures can already do that - as shown by Maine and Nebraska. The legislatures could also choose to give their electors based on a vote of legislature and ignore the popular vote entirely - nothing in the Constitution requires them to do so. The plan by states to give their electors to the winner of the national popular vote is not unconstitutional either - but the plan to work in concert with other states to do so is unconstitutional. States cannot form that kind of compact or agreement without the approval of Congress.
Yeah, like I stated. Winner take all is great if your candidate slides by with a 51% tally.