They want to see and be part of a one-world government. They are consumed with this idea. As a result, they give their power to the Antichrist to make this happen.
NOTE: It says here that God put it in their hearts. This is difficult to understand. The bible clearly states that God cannot be tempted and does not tempt anyone:
13 Let no one say when he is tempted, “I am being tempted by God”; for God cannot be tempted by evil, and He Himself does not tempt anyone.” .
However, I have found that God takes responsibility for everything, even the things the devil does. On the cross, He took responsibility for every sin and evil act that had or ever will be done.