If the wiki was configured to allow anyone to edit, they may have broken ToS at the very worst. Nothing illegal happened.

That's very different than popping an artifactory server with a 0day.

If you take the matter from the spirit of the law perspective, I believe this can be illegal.

IANAL though, this is not legal advice.

A “swarm” and “hijacked” reads like DoS and spam at the very least, doubt any of those is legal in german law.

They murdered Swartz for TOS violations