In an exercise, I was asked to rephrase the following sentence with weil:
Flugtickets kaufen wir am liebsten im Internet, denn wir können die Preise vergleichen.
The correct answer is, if I understood correctly
Flugtickets kaufen wir am liebsten im Internet, weil wir die Preise vergleichen können.
In English, this sentence would be
We prefer buying airplane tickets online, because then we can compare prices.
Note the presence of then, which is meaningful. The then implies some sort of causal relation between the first part (buying tickets online), and the second part (being able to compare prices, which is harder when you buy offline). The sentence without then might be technically correct but seems weird to me, and the same goes for the equivalent sentence in Dutch. There seems to be no element in the German sentence which plays the role of this then (I asked my German teacher about this, but I don’t think I got the question across properly.)
I had to leave early, because then I would have sufficient time to switch trains in Hamburg.
We had to launch the satellite in August, because then we could make use of a gravity assist.
There is a logical relation here, indicated by the then: if I had not left early, I would not have had enough time to switch trains. If we had not launched in August, we would not have been able to make use of a gravity assist. Because then is very similar to in order to.
I often eat bananas, because I like their taste.
I had to go to bed early because I was tired.
There is no then here, and no second-part-requires-first-part relation. I can like the taste of bananas whether or not I often eat them.
So, long story short: how does one say because then in German? And is there a way of saying it that distinguishes because then from because?