Moore v. Harper was just decided by the overwhelmingly-conservative Supreme Court last month, and it rejects this. State legislatures can do what they want, but state judges and federal judges can tell them to go jump in a lake.

Also, representatives are elected popularly, and after the 17th Amendment, senators must be, too. Governors would be tricky for state legislatures to do, because each state has its own state constitution that would need amending—and even states with effective one-party rule still have a difference between a governor and a speaker of the house. Even in a one-party state, no governor would want to be a creature of the legislature.

But is it possible? Sure. If legislatures pass an amendment through their state-constitutional avenues, then it happens. But that’s a high bar indeed. And it might just be completely ignored or dismantled—in Florida in 2018 the voters overwhelmingly chose to amend the state constitution to give released felons the right to vote—then DeSantis did a run-around by miring it in paperwork. The amendment still stands, however.

My illustration isn’t to prove that people aren’t underhanded, but rather that with sufficient masses of people, and with governors who want to appeal to voters, things happen. The whole point of populism is that Guy X’s ranting and raving about “I speak for you” involves voters actually feeling good about voting for him. Put another way, Trump-loving voters love Trump more than their state reps or governors, and as much as they want Trump in charge, they want to be the ones to make him in charge, or else they don’t get to vicariously enjoy what he does.

You're describing the plan in place. Nothing is stopping it - it just isn't finished yet.

There is no federal law prohibiting states from allocating electoral votes with no regard for the popular vote. But these electoral votes are allocated by state governments, which tend to be democratic in nature. States could make laws allocating electoral votes in an authoritarian manner, but politicians who support such legislation would likely lose the support of their largely pro-democracy constituents, and lose their position of power.

In order to effectively subvert democracy, you need to keep the wool over the population's eyes until it's too late for them to do anything. It's kind of hard to do that with something like this.

Keep an eye on fla and Texas. They’ll be doing this very soon.

Any system built on the "best case scenario" is doomed to fail. Remember this well.

Beyond this issue is the issue of the faithless ejector, someone who votes for a candidate other than instructed while at the electoral college. This actually happens sometimes. Usually as a protest. That said, some states do assign some sort of penalty against faithless electors.