The defense eventually scored a club trick for down one.
South gave up a club trick, and West continued with a second trump.
This allowed East to win another club trick, but the contract was safe.
South could afford to lose one club trick but not two.
There was no way that this could produce the required three club tricks.
Any normal play will fail, because of the problems in taking four club tricks.
If he allowed West to win, that player would take two club tricks.
East took his two club tricks and played a third round.
There was no way to take the club tricks, for lack of communication.
He then had time to establish two club tricks and make the game.