DogCow explains his decision at
https://macgui.com/blogs/?e=504. I think his reasoning is totally fallacious. He is closing the vault because having it there encourages people to use vintage software, whereas he would like to see an active development scene, where people use recently developed software instead on their vintage macs.
As someone who would like to develop software for vintage macs I depend on sites like his to get hold of a) the development tools to produce this 'new software' he would like to see and b) the documentation and programming examples that help me make sense of how to do this.
If he wants to encourage an active development scene removing access to one of the few resources that enable this is utterly counter-productive.
Just mad.