Why did he say that the dragon died of bad luck?
It was mainly because when a disaster broke out unexpectedly and suddenly, those with poor luck would tend to be those who were most easily and "unconsciously" hurt and destroyed.
The servant had been "accidentally'" implicated because after the spiritual energy broke through the restrictions on the outer courtyard, the remaining violent energy all surged to the person closest to the gates at that time. As a result, the dragon, who were supposed to have stronger bodies, exploded on the spot.
After the servant was dead, only five dragon youths of the six who originally came to teach Geer a lesson and drive him out of the courtyard were now left. There was only one master and four servants remaining.