Why depopulate? Because they are trying to become immortal. If they succeed, humanity certainly could not survive if no one ever dies - resources would indeed run out. So, they are going to put us all in boxes, use us as lab monkeys for their immortality experiments, and then kill off the remaining lab monkeys if/when they succeed. They feel that they may become God, and that "noble" goal justifies any means necessary to reach it. I think that this makes perfect sense as long as one is evil enough to shake his/her/its fist at the Creator and defile his/her/its works in order to attempt a coup of the Creator himself/herself/itself.