It's not the prime focus, this is true, atagar.
Before launching the site, Assange needed to show potential contributors that it was viable. One of the WikiLeaks activists owned a server that was being used as a node for the Tor network. Millions of secret transmissions passed through it. The activist noticed that hackers from China were using the network to gather foreign governments information, and began to record this traffic. Only a small
fraction has ever been posted on WikiLeaks, but the initial tranche served as the sites foundation, and Assange was able to say, We have received over one million documents from thirteen countries.
There's no reason to disbelieve that claim.. it seems valid to me.