My guess would be that it's mainly a desire for supreme dominance over humanity. These people already have more money than they know what to do with, so there's a natural tendency to lust after things they couldn't have before and use their money as a conduit for power to make those things happen. I think it's why so many of these evil people are fuckin and torturing children to death. To them, the human population has become but a mere plaything, with no real value other than entertainment.

There are several theories, like the elites wanting to end all human existence to "save the planet" and transplanting their brains into robots so they can live forever (Alex Jones believes that one), or to transform humanity into a relatively small population of pan-eurasian negroids to be enslaved by a purebred elite class of Jews (the Kalergi Plan)...