This may come as a surprise but all animals die. Would you prefer they starve to death ?
These expeditions target animals at the end of their life expectancy and if there were no sport hunters the game preserve staff have to arrange to have them killed.
Why ?
There is only so much territory and each sort of animal needs so much.
Cecil the lion who people were so upset about was 35, that's the life expectancy of a male lion. They could actually live till about fifty but because of a shrinking habitat the male lions are killing themselves to claim their space and harem.
Sport hunters provide a needed service, pay to support conservation, support the local economy and even provide meat to the local population.
As I said, don't talk about conservation if you don't understand it.