AFAIK it has always been relatively weak economically - consider that heavy industry used to be a big deal economically, and heavy industry was in the West. But the region did have some high tech industries such as aircraft, optical, electronics. Semiconductors are in that line of tradition.

There also was automotive industry. Audi is originally from Zwickau. There was a BMW factory in Eisenach. Jena was a stronghold for optics and glass industry (luckily still is to a certain degree).