The force of the allegations had been heightened because the dead tycoon had taken the trouble to go on the radio shortly before taking his own life and naming the prime minister.
"They're talking about reform and rooting out corruption," Mr Sung said shortly before taking his own life, "but the first to be cracked down on should be someone like Lee Wan-koo".
The president of South Korea looks on from afar. Literally from afar because she was in Peru when her right-hand man announced his intention to resign.
If she accepts the resignation, her own agony might get closer. She would have to find a sixth nominee in scarcely more than two years.
Three people proposed for the job withdrew their candidacies over ethical concerns and Mr Lee's predecessor resigned after the sinking of the Sewol.