The site, and the extended media presence are full of hardcore racist statements not protected under the German constitution, not considered legal expressions of free speech here. If you have seen the talk, you'd know the site/owner has been investigated by the German inland intelligence agency (Verfassungsschutz), but due to incompetence they only got the wrong person fired... In fact, the "Q&A" intro to the deletion bit, references the executive's inaction.
Some information disclosure is also evidently in the public interest. For example the AfD representatives found are additional evidence for anti-constitutional sentiments within the AfD. This is highly relevant for a possible party prohibition process (which has an extremely high legal threshold).
After all, the website security was hilariously bad. (I suspect the members' IQ scores may have been largely self-diagnosed...) From what I've gathered the publicized data has been somewhat anonymized. The victims of this hack should be rather happy the original data got nuked.
Also good luck extraditing the activist. It's pretty clear the pink power ranger on stage is a borrowed body, and/or, I presume, the voice heard is AI or borrowed recording, as well. OpSec seems alright. But you know, these days, the president of the United States may personally order the NSA and navy seals to snatch the Martha Root off the streets to uphold the holy rule of law and freedom of speech/expression...