I don't think it is realistic for other projects to step in and reproduce or take on a project that has closed.
It really needs new people to step up and take over the projects that that have closed. FOSS is stretched as it is. Of course ask the question, but Divest OS has a community of people who used it - is there no one in that community who can step in?
The whole divestos thing shows the problems with single person or small projects - they're great while they last but people are 100% dependent on that one person to continue. That is a lot of pressure to produce on that one person, but also it is concerning if a popular project fails to grow beyond that one person into a sustainable project particularly over 10 years. That suggests either the person is not able to work with other people or unwilling to let go of control, or the community is not stepping up to help, or a mix of all these things?
There may be other factors too, but an entire security focused project dependent on one person is inherently insecure and unstable. When people are making choices around security I'd suggest an important one is who is running a project and his sustainable is it. Because it's a big ask to keep an OS secure.