We don't know what specifically caused the accident yet. We do know the Captains career is over regardless of the cause. It's still possible the captain did his job well, and still one of his crew members screwed up.
And comparing a ship's captain to a babysitter? When a babysitter comes to my house I expect them to be attentive for 4 hours and then to go home. I don't expect captains to never sleep during long voyages. There is a whole process around allowing the captain to sleep, and waking them for any possible problem, which obviously didn't occur her.
But by all means some posters can compare his job to babysitting.