Familiarize yourself with the idiom. It's commonly used to describe tech companies and organizations with bad leadership:
https://www.theidioms.com/fish-rots-from-the-head-down/
https://www.phrases.org.uk/meanings/fish-rot-from-the-head-d...
It's commonly used in journalism:
https://thehill.com/opinion/white-house/373487-the-white-hou...
https://www.project-syndicate.org/commentary/xi-jinping-chin...
This implies Zig culture is being poisoned by Andrew.
He's the leader, and everyone looks to him. If he behaves like an asshole, and few people call him out or hold him accountable, everyone else thinks that's okay. You then see other members of the community behaving in a similar manner.
Toxic culture breeds toxic behavior and people.
You don't see other open source communities doing this.
Like I said, "rotten from the head". The idiom is appropriate.