[The interior ministry] said the IZH had acted as a direct representative of Iran's Shi'ite Muslim Supreme Leader, Ayatollah Ali Khamenei, and sought to bring about an Islamic revolution in Germany to impose theocratic rule.
The interior ministry also accused the IZH of promoting antisemitism and the Iran-backed Lebanese militant group Hezbollah, which is also banned in Germany and classified as a terrorist organisation by the European Union.
The only concrete thing they seem to have done is praised Hezbollah for resisting Genocide. Of course in Germany that's super antisemitism.
Unless they were planning actual terrorist attacks which it seems they weren't this appears to be Germany doing what Germany does best.