The whole point is Germany did not need to attack any country. No point in starting WW2.
Of course, I agree with it. But could Hitler win? In theory it was possible. So where Hitler had made his main mistake? Capturing Czech part of Czechoslovakia? Apparently no. Major powers just swallowed this act of naked aggression. Encouraged by it Hitler invaded Poland. What one could expect? It can not be regarded as a mistake in the context of Hitler's political line. As for invasion in France then it was apparent success. Hitler went from one victory to another one.
So where he made his main mistakes. I see 2 such mistakes:
1. Heavy bombing of the UK and
2. Too early invasion in the Soviet union.
The first action gave nothing but closed way to honourable peace deal with London that Hitler really needed.
Hitler underestimated Russia (that time existed under name the Soviet union).
As a result Moscow and London became allies, maybe the most strange allies in the modern history. It was Hitler's grave mistake to allow such an alliance.