[The easy answer is that he realized it when everything was crumbling around him, and the conspiracy had been solidified when the shadowy figures pulling the strings from all sides saw fit to capitalize on the rift between him and Gabriel and attack their headquarters outright.

But Jack thinks it runs deeper than that, and if he owes anything to Winston at this point, it's honesty. He seems to consider something for a moment, his face scrunching up as he thinks.]

It's--

[A false start, apparently. Jack shifts where he sits, trying to figure out how he's going to say this.]

One of those things where you don't know how deep in it you are until it's too late. By the time you figure it out, you're already underwater.