Why did countless viewers switch off after 10 minutes of the "Tatort" on Sunday?

The broadcast of a rerun of the "Tatort" episode "Parasomnia" from 2020 led to a significant drop in ratings on Sunday evening. Many viewers switched off already in the first 10 minutes, and this trend continued in the next 35 minutes. An analysis by AdScanner and Vodafone shows that around 13 million households tuned in to the "Tatort" and then turned it off. The disappointment of the viewers probably resulted from the fact that it was a rerun. The episode is from the "Tatort" series Dresden and was first broadcast on November 15, 2020. It has a rather mysterious character than a classic crime story.