> That itinerary that’s “near impossible” with fast flight becomes more impossible with trains that take 2-3x longer.

No because you can actually sleep on the train and be well-rested. Even non sleeper seats are wider and can recline better on a train.

On planes your sleeping neighbor drools on your shoulder and your seat reclines 5 degrees if you're lucky. Sure technically you could take a redeye two nights in a row. If you don't mind being a zombie for the next 2 days.