He returned the heart ten, not the six, and South won in his hand with the jack.
When East won with the jack he made the key play by leading the club five.
South won with the jack and had a communications problem.
He then led the heart eight, which was covered by the nine, and won with the jack.
East played well by playing low, and South won with the jack.
East won with the jack and made the obvious return of a heart.
South played the ten, and West had his last chance when he won with the jack.
He then allowed East to win the second round with the jack.
Next he led a club and won with the jack when West played the nine.
After winning with the jack, East was in some trouble.