The Nazi army, enstead of putting all their resources into killing the jews they could have won the war.

Would the sentence above make a good thesis? Yes or why not?

It's badly written, but does it demand evidence and proofs? If so, then it's good. It's more of a conclusion than a thesis statement.

No, as it's basically incorrect.
You are implying that they used all of their available resources in the destruction of a people rather than fighting a war.
I can think of a lot of people that would disagree with that view point.

No, as it's basically incorrect.
You are implying that they used all of their available resources in the destruction of a people rather than fighting a war.
I can think of a lot of people that would disagree with that view point.
But if it can be supported...

Some research needs to be undertaken on the Jewish Question in reference to the Nazi's and you'll soon find just how flawed that statement really is.

It's not legitimately possible to support a premise when all available evidence points in a completely different direction.