From my scant understanding of the events and the laws, the SEC had an open and shut case to win. Why didn't the SEC try to get a guilty plea, or move forward with the necessary legal proceedings to do so? If the argument is that the court finding Elon Musk and Tesla to be guilty would effectively be a death knell for the company, then I have to ask why the punishment in crimes involving individuals seem so much harsher to me.

To be fair, the SEC isn't the only government body that seems to settle against corporations or sufficiently powerful/wealthy/connected individuals, but the arguments in the SEC's favor seem overwhelmingly clear cut to me (i.e. a "slam dunk") and the topic is easy to follow (a small number of events within a short time frame, a small number of clear and concise legal precedents of the law in question).