It is because Musk is making claims that are not technically possible, and may never be technically possible. Experts have warned him against making these claims, but he is in contempt of them. So, it is no wonder why people are leaving.
Knowing how Silicon Valley operates, it would be likely that he would copy somebody's groundbreaking research (without giving proper credit) and make a few changes (to commercialize it, with gimmicky features) and have his claim to fame.
Knowing how Silicon Valley operates, it would be likely that he would copy somebody's groundbreaking research (without giving proper credit) and make a few changes (to commercialize it, with gimmicky features) and have his claim to fame.