A middle ground solution is for the admins to block the page with a message like "this page is unavailable due to reports of illegal content. if you work for a law enforcement agency and are considering using this as evidence, please contact us" for the preservation aspect.

The meta conspiracy theory in all of this would be that this is an actual CSAM producer trying to take down evidence that could be used against them.

It's very likely that it's someone trying to take down evidence, and since they have CSAM to upload, they would be in deep legal trouble themselves if they were identified.

It is however not at all clear the evidence they want scrubbed from the internet is CSAM-related. It's just the go-to tool for giving a site trouble for some attackers.