FC Schalke 04 | Unveiled: Thats why Mike Büskens doesnt want to be a chief coach

In the final sprint of the 2nd Bundesliga, interim coach Mike Büskens woke up FC Schalke 04 just in time and led to the promotion with a winning streak.
Why does he still not want to continue as a chief coach of the narrow, does the 54-year have?