I'm not sure that's the right wind farm. According to this guardian article, it's actually the Keyenberg wind farm that's being dismantled, a retired site from 2001.

Apparently the site is retired because the operator's permit ends in 2023. Making way eventually for the mine expansion was part of the original deal allowing the land to be used for wind turbines, and so it's not indicative of any change in climate policy from the German government. Additionally the turbines are somewhat outdated, having only a sixth of the power output of a modern one. They would have to tear down and modernise the turbines anyway even if not for the mine.

However from a publicity standpoint it's not an ideal move. Could have given up on the lignite and put new wind turbines in instead, perhaps.