Late Shore,
I can't really say how the change would affect crew moods, especially on a run that’s known for its crew moods. I suspect however, that if the train gets to Chicago ahead of it's 7:00am scheduled arrival and they have to wake up lots of grumpy passengers early, that the crews mood wouldn't be too good after all the abuse they are going to get.
As for why the change, I suspect that there are 2 main reasons behind this. The first is to allow more time to clean and ready the train for it's 7:00pm departure that night, and if something needs fixing it gives them some extra time also. Secondly, and perhaps more importantly, it improves connections with the trains running to the west coast. Currently both the 3 Rivers and the Capitol Limited arrive earlier than the Lake Shore. Amtrak has had several missed connections however from the LSL, due to it's frequent late arrivals.
Amtrak had proposed a schedule change last spring I think, moving the departures up by about 2 hours to improve connections in Chicago. CSX however shot that proposal down claiming that it would interfere with their freight trains. My guess is that this was the only time slot that CSX would give Amtrak, so they were forced to take it or leave it. Why CSX thinks that there is less freight interference at this hour is anybody's guess.
By the way Amtrak always issues a new timetable on the weekends that we change to or from daylight savings time. This both gives them the opportunity to make schedule adjustments and prevents problems with people translating the schedule to/from daylight savings time.