Right now they control the chain of custody and its contents. You dump it all to the internet, and not only would it probably be illegal to download (because of Hunters porn stash), people could also have the chance to plant disinformation, i.e. purport something is in there that isn't, even potentially disseminate an altered copy that makes the "discovery" seem more real. How would this help Biden? By bringing into question the validity of things found in it, which they can then convolute into a mere hoax and use that to distract from the real things discovered.