as if the cards all are supposed to work together.
Thats the beauty of this game
Now, serious. I am very sure the kingdom cards are selected randomly, and the game is just balanced very well. Example: It does happen to me that a Kingdom has a Tunnel but no card to trigger it - things like this would not happen in a hand-selected or scripted kingdom.
On the other hand, all Village-Like cards combo very well with all Smithy-Like cards.