Why is most public office holders betray their oath of office especially at end of tenure?

Question

their integrity, and private life contradict the respect for the office they occupy. corruption, love life, illegal acts on humanity especially in africa

Answer 1

You over generalize.  Really, "most" public office holders do not betray there oath of office.  Some do.  You throw "Africa" into the mix at the end of your question.  That is a different set of folks to pick from.  In much of Africa the current ruler comes from poverty and ignorance.  The only role mode that was available was a previous despot.  In the end, the current rulers take as their example those who preceded them who ruled with an iron hand.  They do what they know.