Luckily, social media wasn’t in play in 1990, and so the spoilers probably didn’t reach too many viewers.
Interestingly, this is not the first time that a German broadcaster has been the source of a significant Twin Peaks leak, although the last incident was quite a while ago.
Given that the mystery of Laura’s death was what drove the series for the majority of its initial run, that was a big spoiler to release.
If such a leak had happened nowadays, the news would be all over Twitter so quickly that even non-viewers would know who had killed Laura Palmer.