Err, why? I've taken my share of commuter and Acela rides in the Northeast and there is nowhere near that level of staffing.
Maybe in the US. In Europe, a train with 500-750 people capacity has one train driver and maybe 3-4 staff (plus on-board restaurant but that's run at a profit). No staff at smaller train stations and only minimal staff at many larger ones.
Maintenance needs staff but that's the same at airports.
The author has some other really interesting (with cited sources) videos about many other transit topics, including how hub-and-spoke/direct played out in the aircraft marketplace, how budget airlines have such great profit margins, long haul aircraft economics, airline schedule methodology, etc.
Amtrak employs ~20,000 people. When you get to the number of annual passengers, and how many trips they operate a year, it breaks down to ~4 passengers per employee per trip.
* Trains ultimately require close to 1 staff member per 4 passengers, much more than a budget airline.
* Unions and legacy salaries further add to those personnel costs. The average Amtrak employee ($75K/yr) nearly makes as much as the average commercial pilot ($77K/yr).
* Since train journeys take longer, the labor cost per trip is considerably higher, especially for long haul routes. When you're doing a long trip like Chicago to Los Angeles, a train takes a lot longer than a plane, so you're paying for yet more labor for that trip. 44 hours of labor for the train versus 4 hours for the plane.
There's a good video that breaks down the costs that make up your train ticket: https://www.youtube.com/watch?v=fwjwePe-HmA&t=29s