I don't think an appreciable number of people were avoiding flying specifically because of the mask rule. The different timeframe on Amtrak makes it difficult for most people used to jet travel.
I'll call Jeeves and cancel the private jet... tell the Nigels I'll be paying $9 for a Dewars in AA economy.
Driving or staying home is an option for many, although yes, Amtrak doesn’t have enough capacity to really matter.