I was thinking of my last question, where I asked if the type of clause after a connective decides the word order and by default the word order after using specific words. After thinking,I realised that there are two words that mean because: one that doesn't change word order and one that sends verbs to the end. Is there any reason be it semantically or etymologically that can explain this?
I do not think that etymology may help here. "Denn" is followed by a main clause, "weil" is followed by a subordinate clause. I (being German) would say that "denn" is somewhat stronger. However, you won't hear"denn" very often in spoken German, usually it will be "weil".
A clause with denn is less dependent of the main clause, which may even be missing or in a separate sentence. The fact that the word order is the same as in a main clause is in accordance with this.
Because of this denn can be used if a clause is not only there to substantiate the main clause but if it's an important statement in its own right.
As a side note, there is a similar pair of words in English: Because and for. Because corresponds to weil, and for (as a conjunction) is similar to denn.
Compare common translations of Matthew 7:13:
[...] Denn die Pforte ist weit und der Weg ist breit, der zur Verdammnis führt, und viele sind's, die auf ihm hineingehen.
[...] For wide is the gate and broad is the road that leads to destruction, and many enter through it.