I mean the decision was stupid from an engineering point of view, but the reasoning is not entirely off. Basically it follows the biological example: if humans can drive without Lidar and only using their eyes than this is proof that it is possible somehow. It's only that the current computer vision and AI tech is way worse than humans. Elon chose to ignore this, basically arguing that it is merely a software problem for his developers to figure out. I guess in reality it is a bit more complex.