“Anyone who believes in indefinite growth in anything physical, on a physically finite planet, is either mad or and economist ,” Kenneth Boulding, environmental advisor to President Kennedy.
A realism to ponder when listening to bankers and politicians.
Preindustrial Craftsmanship 
So, that’s why they invented crashes….. so things can grow again and even more profits can be made by the selected few.
I doubt “they” are in that much control. I think “they” are more like aggressive scavengers. When the inevitable crash comes from a ridiculous system, they pounce greedily onto the carcass and clean up at everyone else’s expense.
I do believe that there are a few groups/families with that much power, yes. These people have gathered so much wealth and thus financial power, that they are able to control or at least influence economies and political systems the world over.