If one wonder why corruption persists in Bangladesh (or any other country) they need to look at the traits of human beings. In a social system where the might and rich are right and have less accountability they want either less corruption, or more chance to participate in it.
Bangladesh is rattling with the recent discoveries of corruptions. If you want to have an idea then read about the Forest King, whom BBC named as cash hoard. This man's wife was changing models of cars many times a year and yet his mother lived in poverty in his village.
Arrested politicians tell about buying support of rival MPs, ex-ministers confessing about taking bribes. Even the ex-home minister took 200 million Taka for saving a businessman's son from murder charge. More shocking facts of extortion were confessed.
Although people question the method but they have full support in the Caretaker Government's efforts to fight corruption.
I hope accountability is established again in Bangladesh and the rot in politics are finally removed. Otherwise the whole society will be infected with the cancer of corruption.