It would hardly take any time to run the trove through a virus scanner, and it wouldn't even need someone to be sitting over it nannying it through the process.

My point is that they shouldn't delete the viruses though. Someone going through the archives probably won't open a random executable from a zip file they stumble across, but a security researcher might want to examine the kinds of malware the leak subject might be exposed to. This is especially the case given we have no idea how many parties (and which parties) had access to these servers.

But why? There's no legitimate reason for wikileaks to do that.

A dump should not be tampered with. How are you going to verify what truly is malware and what is not, and how malware in itself is not of importance?