The Keeper will tell you what happened. I'll tell you what's coming.
A system is not a thing a player believes in. A player believes in the man who stood in front of them and made the system feel like it was built for them specifically. That is the contract. It is personal before it is tactical, and it dissolves the moment the person who signed it walks out of the building.
What gets handed over when a manager leaves is a spreadsheet of positions and a memory of results. What does not get handed over is the specific quality of attention that made a midfielder feel seen during the bad months, or the way a striker learned to trust a role that didn't fit him until it did. That education happened between two people. It is not archived anywhere.
The squad that reached the World Cup carried something earned inside a particular relationship. Not a philosophy. Not a shape. A feeling that the work was worth doing because someone they trusted said so, and meant it, and kept meaning it across years of narrow margins and near-misses and nights that could have broken everything.
The next person to stand in that room inherits the belief's shell. The interior has to be rebuilt from nothing, and it takes longer than anyone in the outside conversation is currently accounting for. The players know this already. They will not say it.
The room is waiting. That is what I can feel from here.