One SEAL put it this way: “I may trust you with my life but do I trust you with my money or my wife?”The implicit message is that if someone's character is such that he can't be trusted in some areas of life, it'll be very hard to trust him in other areas of life, especially when lives depend on the man's character.
I remember back in the 90s having a discussion with someone about Bill Clinton and saying that if a man will cheat on his wife he'll certainly cheat on the country. The fellow I was talking to insisted these were entirely different things. What matters, he argued, is not character but competence.
I think Mr. Sinek would say that that's nonsense.