South Korea Ferry "Accident"

The South Korea Ferry accident was extremely tragic. But was it really necessary to fire the Prime Minister of the entire country because of it? I mean how was anything his fault? Even the subsequent rescue and investigation... how would any of that be his fault? Or could this really be the motivation behind the sinking in the first place? Was the sinking done on purpose? Maybe South Korea does not want to fight North Korea. Maybe a PM change was necessary? There is not enough information on this one-- Wait. The ferry sank on April 15th-- at least it was April 15th in New York at the time. I'm sold.