He tried a diamond finesse successfully, but could not be sure of his ground there.
South led to the heart jack and took a diamond finesse that he expected to lose.
A diamond finesse lost to the king, and West now led the heart jack.
A diamond finesse lost to the king, and West shifted to a club.
Instead of taking the diamond finesse, he had a double shot available.
But consider what would have happened if the diamond finesse had failed.
At this point there was a case in theory for taking a diamond finesse.
South could have taken the diamond finesse now, but he wanted stronger medicine.
If nothing good happens, he will resort to the diamond finesse.
He now needed an even heart split or a diamond finesse.