Oh, one can simply look at a map.
Now this concentrates on military facilities and rail lines. And it is clear where those were. Several times in this thread I have mentioned the "Three train stations", but that was only talking about freight. There was also a 4th station, but that was dedicated to moving personnel and not material.
And look where all of those train stations were, built right against the heart of the city.
Dresden-Neustadt was the main station for freight coming in and out of the rest of Germany (number 3 on the map)
Dresden-Frauenkirche was the main station for freight coming in and out of the occupied areas to the east (number 7 on the map and what the photo I already posted is of).
There was also a large freight station and marshalling yard for segregating inbound and outbound freight, and for movement of freight inside the city itself (number 4 on the map).
There was also a large facility for building and repairing locomotives (number 5 on the map).
Then another main station as well, primarily for moving people (number 6 on the map).
The biggest importance was that it was
the major rail hub in the nation. Not unlike the importance of Chicago and Atlanta when it comes to US aviation.
And being deep in the eastern part of Germany, it was safe from US and UK bombing for most of the war. And as the Soviets never had any kind of significant number of bombers was not really attacked by them either. But taking out those rail depots and facilities was of critical importance to cutting off supplies and equipment from going to the Eastern Front.
As early as the US Civil War, crippling the rail network of the enemy became a key factor in winning the war. Especially for a nation like Germany, which was based on a logistical model that is literally based on US Civil War era technology. Most of their supplies was moved from location to location via rail, then distributed at the destination on horse drawn carts.
Take out the rail system, and nothing moved.