Looking at rail maps from the time, Dresden was one of the three main rail routes to the Eastern front, one through Berlin, one through Prague/Salzberg and one through Dresden. Routes used for moving men and materiel to and from the battle. In 1945 the Germans ability to replace such railways must have been degraded as by that time they had 2 ATAF attacking the rail system in the west since 1944.
With the bombing campaign steel production must have been falling, whilst its requirement was rising.