When Chicago Fire season 15 premiered, the first episode provided answers to all of the questions left behind by the various cliffhangers. Obviously, the biggest question revolved around whether anyone from Firehouse 51 didn't survive the warehouse fire, but there were also major questions surrounding the future of Severide's career, and those questions have returned.
As the new season revealed, Severide ultimately didn't take on a new job with the OFI but instead remained with Firehouse 51. He became the new captain of the squad, which is already a demanding new role to take on. But as Chicago Fire season 15 episode 4 revealed, there was a lot more that went into Severide's decision to turn down the OFI position and remain at 51.
In the episode that centered completely on Severide and Kidd investigating an arsonist, Kidd leans on Van Meter for assistance with the arson case, which gives the pair an opportunity to reflect on the recent past. We learn that Van Meter didn't hear from Severide that he was turning down the OFI job, and Kidd also drops the bombshell that Severide was actually going to accept.

Why Severide turned down the OFI job in Chicago Fire
As Kidd explains to Van Meter, Severide had every intention of jumping into the OFI opportunity, but in the wake of the warehouse fire, he felt that he needed to remain as part of his current team. Severide wanted to stay back with his family at 51 and become the leader they needed. He loves both roles, so it's not like he lost anything by choosing one over the other, but he was ready to choose.
Since Severide and Kidd didn't end up taking in Isaiah again (which had been a big part of possibly accepting the OFI job) and Severide was still with Firehouse 51 at the start of the season, we had all but assumed that we had moved on from that storyline. But it has since returned with new revelations from Kidd. Not to mention, Severide might not have put his interest in the OFI to bed.
We have seen so far in the limited episodes of season 15 that have been released that investigation remains a large part of Severide's interest and skillset. It's no surprise that he was called upon by the FBI to work together on the "perfect" arson case. Part of becoming the leader of 51 was also digging into the warehouse fire and clearing Cruz's name of wrongdoing. He's great at investigating.

That's also why fans have been a bit worried since season 15 episode 4. He could still later decide to step away from Firehouse 51 and take on a new position at OFI. Van Meter doesn't hold any hard feelings about how the initial decision went down, and the door appears to be very much open for Severide to walk through at any point in the future. Will he ever choose to?
Chicago Fire left us feeling unsettled at the end of season 15 episode 4. Severide appears to be the latest target of the mysterious arsonist that he doesn't believe they actually caught. He maintains the nagging feeling that Calloway was the target and now the arsonist has pulled Severide into a new game of cat and mouse. We're definitely returning to this storyline in the future.
But would Severide's future be better served with the OFI over Firehouse 51? What would Severide leaving the firehouse mean for his role in the series? These are questions that will surely be further explored through season 15, including whether there's already a fitting leader in the squad (and in his own household) who could easily take over for him if he ever leaves.
