Frankly, wherever there are fast alternatives, I wonder if the days of airlines are numbered.
Push through rail opportunities like maybe more runs with smaller trains, better synchronization of schedules, quick connections, faster trains etc..
This is the best explanation I can come up with why they're doing it, there isn't really any advantage flying this route. It's not true that people choose the most ecological mode of transport as long as speed is equal or faster, they often have other priorities.
Train travel also has multiple classes of service. And in some ways it's easier to keep people in their own half on a long train than on an A319 where they're only separated by a few feet and a curtain.
So I guess I don't see your point here? Unless you're claiming that terrorists travel first class on trains but can't afford it on planes.