That, I have no idea. Maybe he thought of it as a 'goodbye trip'? Maybe he thought using the "I'm tired" excuse would play out well for the first week after the trip? Maybe he was planning it to be this way? 

Your guess is as good as mine. I've thought about the same thing a lot. I went over the entire trip in my head over and over again and there wasn't really anything weird. 

I mentioned in another post he seemed a little quiet the last couple days of the trip, but he also could have been genuinely exhausted. I know I was.