I think it's that the team needed time to adjust to Koeman's methods.Why is it that Koeman's team (Southampton and us) perform better at the second half of the season?
If you assess his first season at Saints, there was a honeymoon period and then they hit a bit of a roadblock before coming on strong again. That's probably due to Koeman getting used to the league and the players getting used to him. Plus the squad that Poch had had been torn to shreds that summer.
Second season - in many ways - he almost had to start again in terms of several key players (Clyne, Schneiderlin) leaving, and a glut of new signings coming in. So again it was the same scenario really. By the second half of the season they were playing really well and I remember distinctly them hammering us at Goodison last April, and Koeman was furious that they'd only got a point.
So this season, a bit of a dead-cat-bounce so to speak, but the then by December it was clear that some players just couldn't fit (and those are the ones who have left) into Koeman's squad. Still some holes to fill but this season the young players have come in and done just that with more gusto and quality than the tosh before them. Now, the side is fully used to Koeman's style and moulded to play how he wants. At home, we definitely play with more freedom, so hopefully next season we can improve our away form while maintaining our home strengths. With Europe (should we get there of course) there could be a lot of games so a big squad/clever rotation will be important - which means the youngsters that have come in will again play a key part.
That being said, it's key there isn't a huge squad turnaround this summer. Of course, the deadwood will go, but the core must stay (though it looks unlikely I'll admit) in tact for us to at least be able to have that continuity - i.e. not a load of new players who have to get used to the manager's style.