The high irony of the murmurings at the death of Ishmael is that they followed so closely upon the miraculous salvation in the previously mentioned stop. It appears that once their bellies were full, and once they had spent more tedious time on the road, that the memory of their deliverance by the hand of the Lord diminished, and they remembered again only their distress at their loss of Jerusalem and all that it meant to them.
While the daughters and sons of Ishmael were the most logical ones to murmur at the death of their father, Laman and Lemuel are also swayed by the occasion. This is likely partly due to their marriage to the daughters of Ishmael so that they would sympathize with their loss, but cannot be the only reasons, and Nephi was also wed to a daughter of Ishmael. The leadership of Laman and Lemuel in the opposition clearly must be laid at their own feet, and rooted in their own dissatisfactions and dissensions. That the idea of resolving their plight by patricide and fratricide indicate the appalling depths to which their hearts could turn.