Stalingrad was to have been a symbolic and strategic victory for Hitler. That didn’t work out for him.
The best laid plans of mice and men...
Not symbolic, but certainly strategic. The city was vital.
Hitler, wiser than his generals, sought control of the Volga River and the Caucusus.
FReepers must recall that he couldn't get so much as a thimble of oil over the Atlantic. The oil of Ploesti wasn't anywhere near enough to support the war.
Once Germany lost the Battle of Britain and gave up Seelowe, Hitler *had* to go east and at least try to seize the oil of Maikop and Grozny. He was obliged to launch Barbarossa with mere months of supply.
Stalingrad was a vital part of the plan. However - trying to occupy the city was probably a mistake: Hitler might have been better advised to position guns south of the city to stop tankers from traversing the Volga.