The article you cite says his disclosures did not lead to any deaths of any military sources. Many believe Manning's leaks precipitated the Arab Spring which could have a death toll over 30,000. And it certainly crippled foreign relations (with the revelations in the e-mails) and may have made the US military and diplomatic processes somewhat less effective in areas where lives were and are at stake.
Also, whistle-blower laws are not automatic, (and I don't know if they should be). The fallout of the Snowden and Manning handling of secrets emphasizes my point. You have to report the crimes up the proper chain -- merely publicizing things you think may be whistle-blower protected is the wrong way to go about it. There are explicit paths required to report something covered by the MILITARY whistle-blower protection act complaints. Releasing classified information directly to the press or anyone public is simply not protected whistle-blower activity, particularly in military circles.
Lastly, it's not clear there were any war crimes. The Apache attacks, the most-cited "war crime" of many in the Manning list, while terrible in retrospect, are difficult to prosecute, and wide latitude is given to military personnel who believe their actions are legitimate. There WERE armed combatants on the ground, and the cameramen were easily perceived from the air as carrying RPGs rather than cameras. There is extensive coverage of this all around the web, including Wikipedia of course. This certainly could have been a war crime, but Manning could not have been certain.
Manning should have known all of this. He could have followed proper whistle-blower protocol. He chose not to. I'd have much more sympathy if he had originally tried the proper channels and was rebuffed, but that's not what happened (unless I missed something -- I'd love to be corrected here). I've seen no useful analysis of the Whistle-blower mechanisms because people don't seem to actually try them -- they circumvent the laws designed explicitly to give them protection then complain or seem surprised when they don't get that protection.