They usually didn't invent the techniques they used, they usually read underground magazines such has 2600 and the like, and adapted the scripts for their own personal use. Other times they would hear of a security exploit and learn how it use it. The Media and Hollywood have branded these people as hackers, but they are not. The true term for these people are Crackers. They are not dedicated or obsessive about anything but causing destruction.
Crackers are usually Phreakers, phone system hackers, anarchists, and criminals.
They do not fit anywhere in the true Hacker culture. Its like saying that if someone goes to church every sunday that they are a Christian, or if they go to a garage that they are a car. The actual term cracker was coined by the hacker community in defense of sensationalistic journalism. The only people who recognize this term is usually hackers who are trying to defend themselves against the improper use of their brand. Crackers usually call themselves hackers, but true hackers consider Hackers a lower form of culture than themselves.