You wouldn't have to be insane to do these things. You'd just have to have a goal and be determined to attain it. Let's get this straight, early on. What we've seen aboard Horkan's Pride are not the symptoms of insanity; they are only evidence of great force of will. Evidence of planning and execution shorn of any socially imposed limitation. Any mental problems this person was suffering by journey's end are going to be a result of that execution, not a cause.