I think 80% blame should go to Sumon's weird decision not to use 7 overs left to Tapsh and Nazmul. Razzak was being treated harshly from the very beginning, stil he went on! The last over was crucial as it was bowled by Chcha. Though he did reasonably well in earlier overs, but not using Tapsh, a regular last overs bowler for BD, was a stupid mistake for Sumon. I wonder what happened to him? Or was Tapash injured???? Mannn..........so many stupid and suicidal decisions......just look how Aftab got out........having failed to score in 13 balls he went for a wild swing coming down the wicket...........a very wise middle-order batting at that stage, huh?
Sumon should be held responsible, only because chasing 250+ score under lights is never easy for any team at any place against any opponent.