The part in GoT where Daenerys strikes the deal with Kraznys to exchange one dragon for 8000 unsullied warriors, it was an easily predictable risk that Kraznys was sacrificing his own protection.
Before the deal took place and Daenerys asks for all Unsullied warriors, I guessed that Khaleesi ccould turn the same warriors against their old masters. Also, the dragon was hard to train, since she was their mother, thus they won't hurt her. It was an easily predictable scenario and Kraznys failed to see it.
I mean a person so powerful as Kraznys, he must be intelligent to understand the risks. Also, Ser Jorah shows discomfort when Daenerys strikes the deal.
How didn't great master and warrior, ignore such an easy plot?