Sure, but just to add a bit to it there were multiple terror attacks on trains in Europe in recent years. In Germany there was this knife attack just a few months ago, as an example. You also run into some annoying folks on public transport from time to time even if they're not trying to kill you. In those pricey plane seats they're among themselves.

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.