Here you are mistaken. The CEO forms the culture with his behavior, and it was there the moment the papers of incorporation were filed. They were bros from day one, drinking and partying and taking names and breaking rules. Including rules that protect the weakest of us. Companies are fractal. As they are at 5, they are at 500 and 5000.
It always starts this way. You can be a bad person and start a successful company, but that rot never goes away.