A short but incomplete answer is "plausible deniability" - shielding a leader from the details of an operation, either to protect against the risk of the leader betraying details, or to protect the leader from blame if the details come out.
The reason this answer is incomplete is because it implies a level of conspiracy that is unrealistic in most cases - a shadowy group that has everything bad thing planned out to the most minute detail.
The real truth is less mysterious, and more disturbing. What happens in these cases is the same thing we see in our tax laws - loopholes deliberately built into the system. You set up a construct. You break parts of the chain by removing things like oversight, or checks and balances. You focus on the results without focusing on the process. Four words will do it - just wave off the details and command, "Just get it done." And that's basically it - by applying pressure without oversight, you have a breeding ground for corruption. By focusing on the results, you give a pass to the corruption that supplied them. And due to the lack of oversight, you're insulated from knowledge of the corruption.
Corruption doesn't need to be planned - it just needs to be allowed. And that's what happened here. And why is it that the government should be held responsible? Because they allowed to to happen when they knew better. They are basically saying that they didn't know that ignoring the Geneva convention would lead to its rules being broken.
There's a point where refusal to condemn something is the same as condoning it. If it's on your watch, and if you should be able to anticipate the results, then allowing something is encouraging it.