It probably accelerated the decision, but I don't think that's all of it. I think they're moving in the WebKit/Safari direction: open for you to look at, but not really an open source project.
Webkit absolutely takes third party submissions. https://webkit.org/contributing-code/ .
I believe this is an external PR merged a few hours ago at the time of this writing. https://github.com/WebKit/WebKit/pull/66507
Safari does not accept third party submissions, but the chrome has never been open (even before Google Chrome recycled the term).
The open source definition was created in that mind. It does not state or imply open development or a community are requirements.
This is the first time I've seen a project with this much history in community contributions close down, though. I suspect AI will cause more projects to follow in Ladybird's footsteps.
I think your thought was cut off. What is the project no longer?