Why is the shooter involved in the plot against the country?

Question

It is discovered towards the end of Season 1 that Walker is the other operative, and the enabler for Brody to carry out his plot.

However, Brody's reasons for turning against the country are clear due to the loss of Isa, but Walker's are not. The only things we discover about Walker is that he was presumed dead when Nazir and Brody's captors force Brody to beat Walker 'to death', but is never shown attached to Isa or Nazir in any other way.

What is Walker's reason for participating in the plot and going the lengths that he did?

Answer 1

In Season 1 finale, when Brody and Walker meet in the tunnel, Walker tells Brody

“We both got to the same place, Nick. I just got there quicker,”

Keeping this statement, IMO, Walker was turned by Nazir and his men. There are no scenes of him, where he has been shown interacting with Nazir or any of his men, during his captivity, which masks any fact-based inference. He might or might not have needed an Isa for turning on the side of Nazir (which Brody needed). Nazir, very easily asks Brody to Kill Walker, which at least lets me ascertain that Nazir was not close to Walker, like he was with Brody.

Nazir nas his men, might have started with a premise, that his (Walker's) fellow countrymen, did not think twice before almost hitting him to dead, and that they (Nazir and his men) saved him. This might have acted as a starting point, from where they would have systematically brain-washed him!

Well, this is what I think.