The text he wrote makes a lot of sense under that prompt because that prompt provides the frame under which to read it. Knowing the prompt makes it obvious that his general observations happen to apply to Germany and he wasn't aware of that before moving there. He's just polite by not spelling it out.
The real issue for non-publication is the one he cites: "additional reflections in a more personal and light-hearted tone". This matches the general type of content in Zeit Magazin. They weren't looking for a scathing criticism of societal ills but some entertaining piece that goes well with the other easily digestible articles.
Rest assured, he's also trying that route. That mastodon article links to parliamentary requests for clarification of aforementioned quote. In article 1425 he responds (google translate):
"We know that social media and encrypted services are unfortunately largely is used to facilitate many forms of crime. There are examples on how criminal gangs recruit completely through encrypted platforms young people to commit, among other things, serious crimes against persons. It is an expression of a cynicism that is almost completely incomprehensible.
We therefore need to look at how we can overcome this problem. Both in terms of what the services themselves do, but also what we from the authorities can do. It must not be the case that the criminals can hide behind encrypted services that authorities cannot access to."
[...]
"I also note that steps have been taken within the EU towards a strengthened
regulation of, among other things, digital information services and social media platforms. For example, the European Commission has proposed a new Regulation on rules for preventing and combating sexual abuse of children."
[...]
"The government has a strong focus on eliminating digital violations – it applies especially when it comes to sexual abuse of children – and supports the proposed regulation, unlike the opposition."