Brush the dust away

Five Yankee mercenaries have a plan to execute a heist worth of few hundred million dollars and kill a bad Brazilian drug lord. They've really thought it through, they are true professionals, it would be a miracle of anything would go wrong. However halfway through the mission they turn into morons and everything turns to shit. I don't get it how they lost so much potential in so little time in this movie. The first 30 minutes in and I thought I was in a one of the best action movies of the year, but it turned into a pretty laughable farce to be honest.