Why would the black-tailed jackrabbit evolve the following characteristics: large ears to regulate body temperature; long legs outrun predators; fur on the bottoms of feet protect from hot, hard surfaces; digests food twice to obtain the maximum amount of water and nutrition?

Generally, physical characteristics are adaptations to the environment the animals lives in and large ears help the rabbit not get too hot while it's running from the predators: it can also run fast, so those two adaptations help the rabbit survive by escape the predators. Same holds for the fur - it will help the rabbit run faster without burning its feet. Finally, the double digestion helps the rabbit to obtain more energy in areas where food is scarce.