In three no-trump, declarer took the spade lead in hand and advanced the club seven to see West discard a spade. (Yes, a nine from declarer might have avoided some blockage problems.)
East took dummy’s club queen with the king and, though a heart might have been best, chose the diamond 10, which was covered by the jack and queen. Back came a diamond to declarer, who cashed two more rounds for club discards as East let go of a heart.
Declarer crossed to the spade king and called for the club six. If East had played small, declarer would have remained in dummy to cash a spade and play another club. So, East took the club ace and switched to hearts. Declarer played small from hand, and West had no good return after taking his queen. Either major-suit lead would resurrect the dummy and allow declarer to finesse the club nine.
It would not have helped East to cover dummy’s club six with the 10, since declarer could just win and play another club. If East then switched to hearts, West would be endplayed as before. If, instead, East returned a club, declarer could lead a low heart out of his hand.
The defense had gone astray even earlier. Had West guessed to discard a diamond rather than a spade at trick two, a return of either major would have defeated the contract. As it went, West had a second chance after winning the diamond queen. It would have been better to revert to spades, cutting declarer’s link to dummy before the diamonds could be cashed. Thus, the defense would still have exit cards in diamonds at the critical moment to avert the endplay.