Timing the release of relevant information for maximum impact is exactly what any self-respecting media organisation should do.

Your statement only makes sense if Wikileaks had similar information regarding the Trump (edit: or other conservative) campaign and refused to release it.

You conveniently ignore the "political impact against one candidate" bit.

So your statement only makes sense if you assume that all journalists are trying to influence politics to the benefit of their preferred candidate in their reporting.

My point is, unless he also had info on Trump/Republicans, he couldn’t have impacted their campaign. So impact of just one candidate/party was inevitable. Then, optimise for max impact.

Wouldn't it have been dishonest to let people vote before they knew the DNC unfairly treated candidates that polled better against Trump like Sanders despite claiming to be neutral when taking people's money?

Releasing after the fact would have been dishonest and less helpful to either party. It also would have been dishonest to people who donated.

Yes, the DNC chairman resigned and was immediately given the golden parachute of being hired by the Clinton campaign, but the DNC could have made things right instead of that joke resignation. It's not Wikileak's fault the DNC is corrupt and stayed corrupt instead of doing the right thing, and they did the right thing by giving them a chance.