To what degree was Hitler's lack of skill as a military leadership responsible for Germany's defeat?As opposed to other factors like the strategic...

If, when you talk about "military leadership," you include
major strategic decisions such as when/whether to launch major attacks, Hitler's
mistakes were very important.  However, I would argue that they were less important than
his political mistakes.

Hitler's major military blunder was
his invasion of the USSR in June of 1941.  This was something that unnecessary and
overly aggressive.  It turned out, of course, to be one of the biggest mistakes of the
war and can certainly be seen as a major cause of Germany's
defeat.

However, the war was truly lost not simply by this
decision but by at least one other major mistake on Hitler's part.  This second huge
mistake of his was declaring war on the United States in the days after the Pearl Harbor
attack.  Hitler was not obligated to declare war on the US.  While he had been provoked
greatly by US actions, he had not previously declared war and had no need to do so
simply because Japan had chosen to attack the US.  There is nothing that guarantees that
US public opinion would have supported declaring war on Germany in a situation where
Germany had done nothing aggressive towards the US.

Thus,
Hitler's lack of military skill had a great deal to do with the loss of the war, but it
was not as important as political mistakes such as his opting to declare war on the
US.