The same way strapping a gun to a remote-control plane makes the warcrime you just denied (journalists are noncombatants, dickhead) happen, that is to say, it is the tool by which it does. Warcrimes were always going to happen in Iraq, thanks to the Coalition generalship's incompetence.

Killing civilians isn't a warcrime. It sucks to say that, but it isn't. Insurgents not respecting uniform rules unfortunately means identifying bad guys is hard, mistakes get made. The incident in that video also wasn't a drone, that was a helicopter, all parties were present on the battlefield.