Railroads would be going back into the passenger train business if it penciled out.
But it doesn’t. The wonderful passenger service infrastructure that RRs once had was worth investing in when RRs had a virtual monopoly on long distance travel.
Air travel was very expensive then. American highways and autos were a slow option until Eisenhower built the Interstates. This has all changed.
As early as 1920 railroads had 120 mph service between major American cities. They could do it again, but it requires an expensive and continuing investment in roadbed that their current freight service doesn’t.
Passenger rail loses massive amounts of money every time it’s tried in the modern era. Large public subsidies must be built in.
Once it is public, it becomes a target for income redistribution (see Denver RTD recent example). Fares for paying customers go up. Fares for homeless go down, subsidized even more by both taxes and fare-paying customers.
And ridership is falling all over the nation. Uber and Lyft are killing metro area rail. Long distance passenger rail is even less economic.
The only way to make it work is a monopoly caused by shutting down air and auto travel.