I see what you are saying, but look at it from the perspective of the people who want to ensure that every possible copy of their wrongdoing is destroyed. They don't know where the documents are, and in many cases there are documents that they aren't even aware of that show what they have done.

I guess "we need to clean something and we don't know where it is, so we are gutting this place" is a believable reason, but that leaves lots of people wondering why and clever people who know a thing or two will put the pieces together.

Now they can say, "We need to clean anything the Russians might use to out our non-official coverts in the the event they storm the embassy." This is what they did when they all simultaneously decided that online porn sites must purge all user generated content. Just like the Russians here, the fake reason they used was something drastic had to be done immediately to stop illegal pornography. The real reason was the possibility of something being there that would damage their political machine.