Considering that a great many twoofers are teenagers and young adults, if we're talking about members of the movement in general and not just its leaders, I'm of the opinion that it has something to do with the education received. The education many children receive, at the high school level at least, is more about memorization, about reciting factoids pulled from textbooks and regurgitating them onto a separate sheet of paper for a test or a paper, about reading a book to see a certain message implied by the author instead of arriving at the message on one's own. Teachers are becoming more concerned with following the textbooks and are pressured by administrators to tailor their lessons to standardized tests that enable the government to rate their performance with statistics instead of a more nebulous concept that's harder to show in a cut-and-dried form.
Bottom line at what I'm driving at, kids these days aren't getting the lessons in critical thinking and logical reasoning that they should be. That falls by the wayside, as it doesn't really serve the goals they're after with student performance and testing. Plus, a kid who thinks critically and questions things isn't the pliant and obedient student they'd like to have to ease the burdens of student discipline.
One kid finds this "Loose Change" on the Internet and watches it. The kid isn't able to see through the propaganda techniques, deliberate obfuscations and outright lies and errors. They just see one "fact" after another. They have to be facts... the filmmakers seem so sure of it all, as if there is no other conclusion. They're not as prepared as they ought to be to defend their minds against that kind of a pollutant. If they do try to verify what they've seen, they'll very well run into a truthy source that supports the conspiracist view, and feeds them a bunch of other conspiracies they didn't know about. They're likely angsty about the state of things around them, looking to belong to something and be the difference-making person everyone's told them they are, and it all seems to make sense and rationalize everything. How could the government let this happen? It's the same thing as when something tragic happens, and a religious person wonders how God could allow something so bad to happen... except in the religious instance, the answer isn't usually "God could have stopped it, but LIHOP or MIHOP for (insert reason here)". A tr00ther is born... and they immediately attempt to procreate and spread their seed by trying to send their other friends to the things they've seen.