How are flights still this cheap?

Honestly, it's a disgrace - both the insane price differences between plane and train at some points, and the also insane booking procedures in some cases.

Imagine that you'd like to go to, well, let's say Cambridge. That's a bit of a way, yes, but... it would be perfectly possible to do it by train. Quite nice, even, if you happen to travel on a day where you can catch a night train. I'd go to Munich in the late afternoon or early evening, catch the night train there, sleep my way to Brussels. There a little breakfast maybe, then onto the Eurostar to London St. Pancras, and after that it's just a half-hour hop to Cambridge with National Rail.

Easypeasy. Except... well. I can even find the connection I'd like via the bahn.de portal (that is not always the case with more complicated connections), but I can't book it, probably because they are out of contingency tickets for either the ÖBB nightjet or the SNCF Eurostar. So I'd have to book everything separately, which means there's no automatic possibility to take a later train if one of the booked ones is delayed.

It also means making accounts at four different companies, and booking everything separately, which is probably (though not guaranteed) more expensive than having a single thingie. 

While on the other hand, if I'm to book a flight... that is done very quickly, very easily, even if it were with a change somewhere. And it is still ridiculously cheap (thanks to the still ridiculous minimal taxing done on some of the flight stuff). 

So not only is the plane much faster in this case, it is also cheaper, and you have actual hassle and trouble to book a train. Grrr. 

(As you can tell, I am not amused. Even though, in this case, it will probably end up being the plane anyways because of it being much faster, I would really like the two possibilities to be a little more evened up, regarding the ease of booking and the price.)