Whatever the reason, politics, religion, power, what pushes people into extremism?

I suppose it would help to define “extremism”. Are you referring to holding beliefs that are far from the mainstream, or are you referring to behavior?

Personality type and mental heath.

@hominid how about both, do you really need a more detailed version of extremism?
How about someone who would love to put a bullet in your head for failing to see the world as they do, that extreme enough for ya?

@Coloma that is fer sure, but there seems to be an awful lot of people out there that fit that bill.
Is there anything society can do to help them before they become extremists?

Need. Desire for attention. Lust for power. Some degree of irrationality. A simplistic view of life. Inability to get along with others.

Excitement.

Anger

In many cases, it’s a lack of cognitive flexibility, i.e. an inability to see a matter from more than one perspective. F. Scott Fitzgerald said that “The test of a first-rate intelligence is the ability to hold two opposed ideas in mind at the same time and still retain the ability to function”.

Someone without much intellectual firepower may base their worldview mostly on what resonates with them emotionally. If the basis for your worldview is emotional, than you won’t be able to open yourself to other perspectives. You will come up with (or, more likely, borrow) enough rational sounding arguments to make it sound like you came by your views through a reasoning process, but they’re really just there to lend some apparent substance to your emotion-driven positions. And because your emotions are strongly invested in the position, you’ll react emotionally toward opposing views. This leads to a situation of polarity.

Ignorance

@thorninmud so die hard conservatives fit the bill well then??

Alas, it cuts both ways.

Someone started passing that debunked, out of context video about Obama’s views on “World dominance” again. I posted a link that showed that it was misleading. The next person after me posted about how horrible Obama was. I don’t see how they can miss my post! It features a link that displays the head line in great big letters, that it was a “hoax.”

Trauma.

Delusions of grandeur.

You’ve answered your own question by describing such people as nut bars but I don’t think that is always the case. Desperate situations can push ordinary people towards extremism. History is full of examples.

I Think some people feel passionate about certain issues & it becomes an obsession for some reason.

It appears from the first two new episodes of the“Homeland” series, in which a young Muslim student’s entire family attending a wedding is killed in an ill-conceived drone strike, that this question will be explored this season.

Please watch this stunning 9 minute video on Vimeo Regolith .It is about e-waste scrap workers in Ghana. It is one of the best examples of how honest young men spend their lives in that area.
While watching, think how easy it would be to turn them around and into terrorists or extremists. What do they have to look forward to? What property do they own? What are they thinking when they see the goods discarded by westerners?

Then think what the world needs to do to break the cycle.