But Elon and his sub....
As an engineer I disagree. His proposal was pathetically devoid of any of the mission's basic requirements and feasibility analysis, and in essence boiled out to nothing more than a maketing ploy to promote his own public image.
Pulling that stunt at the expense of a disaster that could have ended with a dozen deaths speaks volumes about his character, as does is smear campaign targeted at one of the divers which went to the extrene of Musk himself accusing him of being a pedophile.
To use the lives (and potential death) of children for PR is abhorant.
Anyway his mistake was that he used a start-up mentality in situation that was not a start-up. You do not try to capture any market, or anything like that. You just want to follow the safest path, the things that you used, understand and that work.
You can be sued for watering your flowers too much.