Photo: JoJo Whilden/SHOWTIME

***This interview contains spoilers from the season four finale of Billions.***

Just as we were getting used to the idea of New York State Attorney General Chuck Rhoades Jr. (Paul Giamatti) and hedge-fund billionaire Bobby “Axe” Axelrod (Damian Lewis) playing nice with each other, Billions responded with, “Eh, not so fast.”

In its season-four finale, the Showtime drama recalibrated the positions of several of its main players, most notably by shifting the dubious alliance between Chuck and Axe back into a full-on rivalry. After celebrating a victory over season-long foes Attorney General Waylon “Jock” Jeffcoat (Clancy Brown) and U.S. Attorney Bryan Connerty (Toby Leonard Moore), Chuck needs someone new to take down, and he has set his sights back on Axe, who he feels has been pulling the strings of his life for far too long.

The episode “Extreme Sandbox” also saw Axe’s relationship with venture capitalist Rebecca Cantu (Nina Arianda) become collateral damage in his ongoing war with former protégé Taylor Mason (Asia Kate Dillon). Meanwhile, Chuck’s marriage to Axe Capital performance coach Dr. Wendy Rhoades (Maggie Siff) is in tatters again, the lowest blow being Axe using his monetary muscle to get Wendy’s medical license reinstated. Both Axe’s and Wendy’s newfound singledom also raises the question as to whether this platonic relationship is about to move into something more romantic.

Prior to the airing of the season-four finale, Vulture spoke with co-showrunners and “Extreme Sandbox” writers Brian Koppelman and David Levien, who recently signed an overall deal with Showtime to develop new projects exclusively for the network. Here they discuss their reasoning behind some of the episode’s major creative decisions.

This interview has been edited and condensed for clarity.

I think this was the strongest season of Billions yet, in which Chuck and Axe were, for once, working as allies. So why make them adversaries again?

Brian Koppelman: It goes to who these characters are and what drives them. We start by asking ourselves questions; usually, we lead from a place of curiosity, so it’s not like there was a strategy. We knew at some point they would be turned toward one another again, but as we were writing the season, it just became clear to us that these two alphas, in the way that they’re alphas, how would they really coexist when each needs to make the world in exactly the form and shape that they see it to serve their own need? How are two people like that going to just coexist peacefully? It doesn’t seem that they ultimately, long term, could.

I am still processing Chuck’s big reveal of how he finally got his revenge on Jock and Bryan. How did you come up with — and keep straight — all the intricacies of Chuck’s season-long entrapment scheme?

David Levien: Well, it wasn’t just us. The writers’ room really pitched in coming up with the bones of this overplot. And then we have lots of meetings about the flashbacks and how each piece of it would reveal something, so that as we were shooting each place, we could be as efficient as we could and get the flashback pieces without having to go back. So, we’d been planning it along the whole way.

Koppelman: We would be working with and telling the actors about it too. The primary players in the con were Chuck and Charles Senior, so Paul Giamatti and Jeffrey DeMunn. So we were, from the beginning, letting them know, “Okay, this is the moment you start working together.” The actors were able to play this stuff being aware of what they were doing. We’ve been thinking about this our whole lives: We wrote Ocean’s 13, and we did the thing in season two with “Golden Frog Time” [a.k.a. the Ice Juice scheme]. The Sting was one of our favorite movies when we were kids. We’ve been studying how to do this for a very, very long time.

I loved watching Bryan Connerty slide from being an idealistic lawyer into a vindictive one. So is this it for Connerty? Or do you think he has it in him to make a comeback just like Axe and Chuck have over the seasons?

Koppelman: You gotta keep watching the show. We never speak to which way the future is going to go. Partially because we haven’t written season five yet. But Toby [Leonard Moore] is so smart. After reading episode 11, Toby came to the two of us and said, “Just tell me one thing, mate. Am I ‘the Idiot’?” And we said, “You are, sir.” And he went, “Oh, fantastic! Great!” He was so excited to play it. He loved the whole idea that Bryan Connerty had gotten himself to a place where he couldn’t see what was about to happen. Toby loves playing that stuff. He’s been a wonderful partner to work with.

Photo: Jeff Neumann/SHOWTIME

Axe had a great thing going with Rebecca, but for the sake of the story, I understand why you had them to break up — a quintessential element of Axe’s character is he cannot let that kind of betrayal go. Did you debate different ways of solving this problem, or did you know right from the start that Rebecca wasn’t going to last?

Levien: Nina is such a brilliant actress, and she made that Rebecca character such a great complementary piece to Axe, and she fit into the world so well, but as the pressure of these business things heats up, the tensile strength of the relationship gets tested. So it becomes a question of not whether she’ll be back but in what capacity. Can a relationship survive? Axe laid it all out there in that very dark admission. It wasn’t just lip service that he wanted to lay it out there to see if they could go forward from there — he’s a smart guy. He knew the answer was probably gonna be no, but he wasn’t hoping that. But, if he sees something as a betrayal like that, it starts to get binary, especially if there’s a huge business piece on the table in the middle of it.

You’ve spoken before about how some of the story lines this season were written and shot well before real life turned them into “ripped from the headlines”-type episodes. [Editor’s note: In the season-four premiere, David Costabile’s character, Michael “Wags” Wagner, is kidnapped at the embassy of a fictional Arab nation.] What do you attribute that to?

Levien: We pay attention to the world of business and politics, so I guess it’s just a question of getting on the frequency. We would’ve never wanted to have been right on the frequency of where such a terrible thing would happen, like in the Saudi Embassy, what they did to [Jamal] Khashoggi. Unfortunately, it just made the thing seem just more credible in the way the world works. And something Brian said in an interview recently, was, at first, when we were making the show, people might have thought that it was hyperreal, but the way the world has changed now, they understand that it’s really just the way it’s happening.

Season four gave us a lot more insight into how emotionally damaged Chuck has been since childhood. I admire that he still wants to “do good,” but is that even possible considering everything he’s done and how self-serving he is?

Koppelman: I think that’s for you to speculate. You’re exactly right, you just laid out the central question for Chuck going forward. He’s always wanted to be the best version of himself he could be and to escape the damage of his childhood. But whether he can, well, you know.

Where is the Rhoades marriage at this point?

Koppelman: I think all I can say about that is, to quote Pete on Mad Men, “Not great, Bob!”

How did Chris Carfizzi, who plays fired Axe Cap employee Rudy, end up showing off his opera skills in the finale?

Koppelman: If you’re Dave and me, and you find out that Chris is an opera singer, how are you not going to use that?

Levien: Yeah, we joke around that we’re like a snout-to-tail operation. Like any special skill that the actors have, eventually we’re gonna get it in there. We were out in L.A. for the TCAs, and we were going to meet up with Damian, and he said, “Meet me on the tennis courts, I’m taking a lesson.” And as soon as we saw him hitting those looping forehands, we were like, “Bobby Axelrod’s playing tennis with somebody incredible. And we’re gonna do it without a body double, it’s gonna be Damian Lewis playing.” So then we just figured out how to get Maria Sharapova. Basically, if you reveal something, we’re going to use it.

What can you tease for season five?

Levien: A lot of ins, a lot of outs. A lot of what-have-yous.

Koppelman: This season was very Billions. Next season is going to be very, very Billions.