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.
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
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.