Without assigning blame to anyone, a simple-to-follow best practice would be probably to just never hand over a (personal) project. Make it as deprecated and let the community fork it. If you feel like it, point to the new, maintained fork.
> lets roll for a bit with the assumption that a small amount of extra care on Tarr’s part could have avoided this mess.
Are you kidding? The bare minimum of not just handing a repository under your name to a random stranger is apparently a hard to fathom concept for this author.