Why any document dumps?

Just a quick question about the US Attorney purge investigation now underway.

The White House is being awfully secretive, invoking executive privilege on an unprecedented range of topics. They may or may not have "lost" over 5 million emails, some of which may contain damaging information. And yet there have been several "document dumps", releasing several thousand pages of emails and other documents related to Department of Justice communications.

My question: Why? There has been some damaging information in the document dumps. Why have they bothered to cooperate at all, when they don't have any shame about flagrantly disregarding Congressional requests and even subpoenas?