What is happening to good old language C?

"The programming language of all programming languages C is consistently going down since November 2015. The language was in a range of 15% to 20% for more than 15 years and this year it suddenly started to suffer. Its ratings are now less than 10% and there is no clear way back to the top. So what happened to C? Some months ago we already listed some possible reasons: it is not a language that you think of while writing programs for popular fields such as mobile apps or websites, it is not evolving that much and there is no big company promoting the language. May be there are more reasons. If you happen to know one, please share it with us." I found this question in the December 2016 TIOBE Index. Now please, let's not argue about how wrong the index is, I know, but still such a large plummeting does not make sense unless they recently changed their methodology, which they did not. So, what might the reason be?!