Same reason there always is; we struggle to make 80 points.
A fair point, but the youth team wasn't Wenger's domain. Equally, scouting is all very well, but as other clubs wised up to what AW had achieved, competition for the good young players across Europe hotted up and money (ie Chelsea) tended to talk.
Wenger was a master of implementing a good scouting network. A blue print for others to follow and they did with more money. He was not a master of spending big and not one for developing youth.
So what next?
He kept us ticking along but with a combination of transfer restrictions and his own limitations, what were we really capable of achieving?