I think it acknowledges a failure in explanation -- you start with, "The talks failed because...", but there is no easy reason why the talks failed. So you just

I think it acknowledges a failure in explanation -- you start with, "The talks failed because...", but there is no easy reason why the talks failed. So you just put a word in there. "Politics." It's an aborted attempt at explanation. It implies extensive context and a truly complex or even incomprehensible explanation. The grammatical failure is the kind that would happen in speech, when the speaker suddenly realizes he's bit off more than he can chew, and truncates his explanation with a pause, a word, a shrug, and a rueful smile. "because, you know... politics."