Looking at the line of succession, why do you think the cabinet members are listed in that particular order?

The cabinet is placed in that order because according to the chronological order of their department creation or which department will be their successor. For example departments of human services and of health being a successor to the department of education, welfare and health. Department of defence being a successor to the department of war.

The line of succession is the order of how persons may become or my actions as president. A president who is incumbent becomes incapacitated or resigns or dies or impeached by the house of representative then a line of succession is set by the constitution and presidential act as amended to include new offices for the cabinet. The succession follows the order from vice president, it goes to the speaker of the house to president pro which is for Senate and at the end, it goes to federal executive departments who then form the cabinet.