There is some truth at the center of every conspiracy...at least a nugget of truth. Of course, this gets taken to the extreme so that people believe it to be gospel (intentional choice of wording). Beliefs are a funny thing. Most things people believe, they have no idea how they got there, it is indoctrination. However, others purposely choose a belief system which, in the end, is something they will fight to the end defending.
As for science, be careful pointing to that. The proponents of what you discussed use science to justify the say way you use it to negate. And let us not forget science was used to prove the Jews were a lesser race and deserved slaughter and that blacks were not as smart as other races. The manipulation of science is age old (and only getting worse).
Many have made a great living off the conspiracy industry. Guys like Icke have been espousing stuff for 30 years. Of course, over time, much of what he says was proven correct, hence it must be a worldwide conspiracy. What actually is happening is a natural result of a capitalistic system gone out of control. Perhaps this is the inevitable end to a capitalistic economy, I dont know. Either way, greed is at the core of much that is taking place and a money driven system results in the "elites" profiting while enslaving everyone else.