I guess he was aware of that , when it will be not running good that his job is in danger.
Also i dont agree with you on the case when he will be win the german league at his first year , if that would be happen its a very good achievement for him and the Club.
About the Champions League and winning it why should it not be possible ?
Winning the league is realistic, I think the Munich management gives a target according to the team's condition. Kompany has been given enough funds, he is given space to choose players according to his wishes. They should be able to learn from last year's mistakes. Management also has to be wise with the coach, I think the change of coach with a short term is also bad.
As for UCL Munich, they are an experienced team, so I think they are able to compete. But the current condition I am quite doubtful that they are able to win.