Why BCB get this Decision?

After back from Zimbabwe the team management of Bangladesh gives their report to Bangladesh Cricket Board (BCB) about the bad result of Bangladesh Cricket Team against Zimbabwe. In this report they said Shakib Al Hassan & Tamim Iqbal not get seriously in this series. They think they won this series very easy. And their captaincy is not good in this series. So BCB get this decision that now Shakib & Tamim is not Captain and Vice-Captain of Bangladesh Cricket Team.