That was an example of a train going slower on purpose to let people sleep a full night. A regular high-spees train could do that trip in 2-3 hours, beating a 1:15 flight in convenience by a huge margin.
Maybe you can but none will recommend that you do, for example Paris recommends at least 2 hours [0]. And if you need to check luggage you have no chance if you're only 20 minutes early, on a train you just carry it onto the carriage.
[0] - https://www.parisaeroport.fr/en/passengers/flight-preparatio...
It was called iDNight, by iDTGV, a former low cost high speed train operator in France. The idea was to run high speed trains at a slow speed during the night, turning a 3 hour trip into an 8 hour trip so that you can get a full night, and also so it can leave as the departure station is closing and arrive as the destination station is opening, therefore exploiting downtime, I guess.
These were not sleeper cars but regular high-speed train cars, not ideal for sleeping, but since most seats were vacant, at least in my experience, you could easily get two seats for yourself.