Hi. An experienced 4Shared user here. I've got a collection that goes back as far as July 2017 and currently have over 50.000 private videos and photos from private users. I made this account, in particular, to point out that your claim isn't true.
First of all, all data collected by the 4shared algorithm to contain nudity on 4Shared is protected by age confirmation. 4shared definitely allows nudity. It even age-restricts things considered nudity.
So as to why all links go private (and require access) or simply vanish, is not because 4Shared kills and/or inactivates the content:
It is because the USER/UPLOADER is made aware that their photos/videos are being saved.