I'll start the brainstormiung.
The implosion story is a cover up and they actually entered the hollow earth through an elaborate system of locks and dams in order to meet with Peter Viereck, who has been reigning over the sub-subterranean ape people as a tyrant since 1952. Using the mystical power of orgonism they will return to the surface and subjugate humanity to build a giant crystal pyramid from which they will fight the Posada aliens. Our Orca comrades are trying to stop them by incapacitating their agents off the coast of Gibraltar.
The easiest one for me is a bunch of rich billionaires decided to fake their death and cash out some life insurance.
They could be full Larry Hilblom on a pedo island
You've got to go deeper. What are they using the money for? Clone an army of Alan Greenspans to force the market to behave the way the Chicago School thinks it should? Giant blimp made of cocaine from which they'll bombard the working class with killer job-application web portals? Unleash your imagination!