It's also very poorly interconnected. Going Stockholm-Hamburg is one flight. Or 4-ish trains with uncertain interconnections and some busses in between IIRC
Edit: Looking at bahn.de, I found a direct train from Stockholm to Hamburg,[1] no need for a change in Copenhagen. There was also an option to change in Malmö instead of Copenhagen.
Love to see a comparison of trains vs air travel here. My last few trips have had around a 50% success rate for flights.