This was millenia ago in a culture that didn't write anything down. Who knows what anything was like then? To fill in the gaps we end up using our own modern biases and narratives. We like to think we're better and more rational than people in the past, so we attribute these mutilated bodies to a motive that we've moved on from (ritual sacrifice), rather than a motive we still have (judicial execution). To be fair, ritual sacrifice did happen in some cultures and was well documented, but who knows what was going on in this case?