IMO the whole club, players, board, manager coaches etc knew this would be a tough season and the objective was to reach 40 points.
Once we had done this, it was difficult to motivate everyone. Also, we had been to a Cup final which was a bonus. So, our season simply petered out. If you think we were the only ones, well look at WBA. They reached 40 points in late January and thereafter put the deckchairs out. The fact is that clubs like Saints have only really one aim in the league, survival. Once achieved their is little incentive to push on. That is why in the middle of the league there is so little difference. The only competition is in the top 5 and the bottom three or four.