In general, I think these things just happen when the packages are ready. In the early days of Julia, a lot of repos ended up in organizations, and now a lot of organizations have a bunch of effectively abandoned packages.
I am not sure I understand the reasoning here. From my perspective, clean code, good documentation, and responsive maintainers invite contributions. These are pretty much orthogonal to repos being in an organization.
If anything, I find it easier to contribute to package which has a single main contributor who has a vision about where the package should be going. A lot of PRs just sit around for a long time because no one is willing to make some major decisions (which include just saying no to a PR, but quickly).