When MDN shows me content in German the first thing I do is switch to English to lower the cognitive load.
I can just speak for myself, but jumping back and forth between two languages is adding unnecessary cognitive load.
I also never ever heard someone talk about the "Meisterzweig" in a Git repository.
For me part of the reason most people use English in CS boils down to the English textbooks being better.
Also there is no need to translate technical lingo if everybody understands it. More general IT terms are translated sometimes (e.g. hard disk = Festplatte, keyboard = tastatur). I'm sure a linguist could explain why it happens in some cases and not in others.
And if I were to try to translate "master", it would end up translated as a word that could be equally well translated back to English as "lord", which is just silly.
Generally, abstract or mathematical concepts tend to have German words, but even those aren't always used. Things specific to tools/technologies typically don't, and few bother coming up with German equivalents. And German doesn't mind integrating other words, even mixing them in compound nouns with German ones.
People like to use the terms/style they are most familiar with. (See also: how über/ueber turned into “uber” in english.)
I think the age of the term and the age of the speaker matter a lot.