Hard question to respond to simply and succinctly.

Shotgun thoughts:

-I think it is a complex mixture of motives and incentives. There are power hungry and evil people in all levels of society and governance. 
-As far as being captured goes, I would say this is true ideologically, via bribes, or via blackmail. 
-There's also the global fiat banking cartel. too many world leaders have their hands tied by the IMF via debt restructuring conditions. -Then there's groups like WEF. Klaus Schwab has also publicly boasted about WEF protiges *infiltrating* political cabinets all over the world.
-I think a lot of people in the lower ranks of the global cabal probably think their going along with tyranny will also allow them to escape the worst parts of it. 
-There are also a number of world leaders who don't have children, so that is a factor too.
-Underneath all of this is spiritual warfare. Satan and his demons hate God and therefore hate humans who are made in his image so they decieve and pervert and corrupt with the intention of destroying us. Many people, including some of the most powerful people in the world, are their puppets. But I would be remiss to say that and leave off that all tyranny ends, all tyrants die, all towers of babel fall, and, sooner or later, reality reasserts itself. The reality is that Christ is Lord.