Well, for one, I don't understand it either, why Merkel didn't see the change through. It was, however, started by the red-green government before Merkel. They set up the system which guaranteed a price for any renewable energy producted (initiall very high, decreasing for later installations).

The production did indeed skyrocket, with the peak of over 50% renewable power in 2020. But in the last 3 years the built-up of new wind generators has stalled. Hitting a peak of 5GW/year in 2017, it went down to below 1 in 2019. This was due to several changes by the government. On the one side they replaced the flat fee which was paid for electricity produced to a complex auction schema, on the other side there were more and more restrictions about where one could build wind generators. Also the amound of solar power was even capped. It seems that the situation has improved somewhat, the build-up of renewables was a bit higher in 2020 than in 2019, but hasn't reached the past peaks again yet.