Based on my understanding they were simply better managed and benefited from some cross border stuff that exposed them to other markets that weren't readily available to everyone in Russia.
Similar to other states that had some association with the west where in the end they could sell products and goods outside the planned economy and that helped keep things going.
I think the GDR was just a more effective country, just like Czechoslovakia and Hungary were. In the case of the GDR, despite being led by a very small-minded clown basically sanctioned by the USSR. Russia has never had it good in hundreds of years and it kept the tradition under communism.
