Whoever it is, that's always the case in government. It's not their money and any accountability like this is so rare, that there's no need to do things like audit the books or to ask that there be a documented reason why this particular cop needed to do all that OT. The chain of responsibility just abruptly terminates with someone who has the prerogative to approve things without explanation, and that person doesn't (legally or department-policy-wise) owe anyone an explanation, and he won't give one. (Because usually the answer is "Because he's in on the scam himself")
Note: I'm not saying that every civil servant scams. Far from it. I'm saying that conditions are nearly always ripe for this type of thing because those in charge won't be held responsible, and those at the very top are elected officials, who are in more and more areas only vulnerable to primary challenges. So if you have a good enough rep for "supporting team blue/red" you can cruise past plenty of oopsie-daisies like this by just scoring cheap political points.