Answer:
The adage "The wider... the Nazi land endeavour, the greater... their final danger" refers to the Nazi regime's growing financial and logistical load as it engaged in ground warfare and territorial expansion. The Nazis' desire to conquer more land meant that they would have a harder time keeping those lands under control and would be more vulnerable to outside threats and resistance. This would ultimately result in their defeat and doom. The statement implies that a land-based war was not feasible for the Nazi regime and that in order to have a chance of success, they needed to concentrate on dominating the seas.