If Hitler had controlled the strait of Gibraltar, there would have been the following consequences:
1) Hundreds of thousands soldiers and tons of material free from waiting for a possible invasion on the shores of Italy or the south of France.
2) German and Italian armies could have beaten easily the English forces in North Africa. English government could still have supplied its armies by the Suez Canal, theoretically. But it would have been much too far to let them be able to sustain a war. So, quickly, English forces would have been defeated and Germans would have taken the control of the Suez Canal also.
3) Then, the Mediterranean Sea would have been totally free of Allies forces. It would have become a German sea.
4) German forces would then have had access to the oil of Iraq, Iran and Saudi Arabia. Then they wouldn't have got to worry about the oil of Caucasus. Thus, Hitler the jew couldn't have justified his huge strategic mistake of concentrating his forces in Caucasus and not against Moscow.
5) The oil of the Middle East wouldn't have been available for the Allies anymore. The USA supplied GB with its oil. But oil from the Middle East was probably used to supply British armies on the Asian front.
6) The supply lines of the English armies regarding their Asian empire would have been much longer. Thus it would have been much difficult for them to win battles against Japon's forces.
7) There wouldn't have been the invasion of Sicily, Italy and South of France. And Hitler wouldn't have had to send tons of material and soldiers in order to defend these areas. And Hitler had to know that there was an important danger on this side, since England controlled the Mediterranean Sea.
8) Thus, the war would have lasted longer. It would have been more difficult and longer for the Allies to win. Or the plan of Jewish leaders would have been less coherent.
So, because of the troops and material economized, the access to Middle East oil (and the loss of this oil for the Allies), the strategic implication about the war against Russia, the possible loss of his Asian empire for England, controlling the strait of Gibraltar was absolutely crucial for Hitler.
But, as Hitler was in fact a Zionist jew, he had to avoid obtaining the control of it.