No, I didn't interpret it as insanity caused by the losses alone, just the physical and emotional damage caused by being responsible for a catastropic battlefield loss (which could arguably be a cause for psychic trauma for someone with an ego as large as his), exposure to the elements (being left stripped on the battlefield with corpses all around), and, last and probably least, the guilty knowledge that his scouts had told him not to attack and the fact that he'd so badly bungled the whole situation, resulting in the death of his five companies, his brother, his brother-in-law, and his nephew.
Gotcha. Good point.