They didn't actually release information that was harmful to the DNC. They released harmless information with fake Russian fingerprints to distract from the actual real information which they knew was coming which was extremely harmful to the DNC, Hillary, Obama, and others.
To give you a Tl;dr:
They didn't actually release information that was harmful to the DNC. They released harmless information with fake Russian fingerprints to distract from the actual real information which they knew was coming which was extremely harmful to the DNC, Hillary, Obama, and others.