CTOs aren’t always super-technical-and even those who are, while the CTO of a small startup might realistically have an expert-level understanding of all the business’s core technologies, that is no longer a realistic standard when talking about a multi-billion dollar firm with a highly complex or diverse tech stack. Arguably, one of the most important tasks for a CTO, is to be able to tell the difference between good engineering executives and bad ones. And, judged by that standard, Musk actually has done a very good job as SpaceX CTO, much better than many of its major competitors. Doing that requires understanding the technology well-enough to distinguish engineers and engineering leaders who really understand it from those who are just pretending to do so-and I think it is obvious Musk does understand the technologies at SpaceX (and Tesla too) well-enough to successfully make that distinction. People seem to be holding him to an unrealistic standard, which I doubt they’d actually apply to a CTO who wasn’t named Elon Musk.
What about Larry Ellison, CTO of Oracle? Frankly I think Larry Ellison could say any crazy thing he liked, and no one would really care, and he'd stay CTO and chair of Oracle's board. Because C-suite executives get a "free pass" all the time–especially when they combine their C-suite role with a substantial ownership interest in the company (true of both Ellison and Musk). But most C-suite execs, the average person has never heard of them, and so they don't care what they say. Whereas, Musk is a controversial celebrity, so people judge him by rather different standards than the thousands of other near-anonymous CEOs, CTOs and billionaires in the world.