i misread that, and thought the entire country was going to implement it. this really does make a lot of sense (in this particular city). but i woudn't go around and limit traffic in every city to 30km/h like some politicians in germany tried to do.
I'm not aware of any german politician wanting to implement a general speed limit of 30 in every/any city. Instead there is an attempt to allow cities/mayors/city planners to implement speed limits on individual streets for a variety of reasons. As of now many reasons like noise, risk to other road users, even schools/kindergartens in the vicinity are often not sufficient to warrant an individual speed limit according to road traffic regulations.
30kph in every city centre makes sense. It's safer for everyone, including drivers. Nobody wants to hit a cyclist or pedestrian and you can see more at this speed, and have a shorter length to stop.
It also encourages people to take ring roads if they need to be on the other side of a city and need to have their car there.