Todd didn't know about the threats that Dry City had been experiencing recently. After all, these problems had only started to appear recently, from about two months ago to now.
On the other hand, although Todd's family and Black Plain were business partners, one side had no obligation to communicate to the other about problems of this nature. That is, the Dry City had no responsibility to help the Cohen family in difficult times, just as such a noble house did not have to send forces to support the territory of Minos.
Obviously, there was goodwill on the part of both sides since they had had mutually beneficial times. However, for a greater connection between these powers, it would be necessary for their relationship to move beyond something purely commercial, as it had been until then.
But before something of this nature could happen, one side would not interfere too much in the more private affairs of the other.