Leonard was one of three coaches, along with Luke Steckel and Joe Woods, to be retained by Klint Kubiak from the previous coaching regime.
Kubiak and Leonard have a mutual connection through Seattle Seahawks Head Coach Mike Macdonald. Leonard served as an outside linebackers coach under Macdonald at the Baltimore Ravens during the 2022 season, while Kubiak notably won a Super Bowl with Macdonald last season as the Seahawks offensive coordinator.
"With obviously the backing he had in the building, the relationships that he built, and then when it came time to interview Robbie [he] was impressive," Kubiak said back at the NFL Combine. "He had a plan. He knew what he wanted to do, he knew the type of players he needed to do it with and it just revealed itself to me that he was the right guy for the job."
As for Leonard's plan for the Raiders defense, he was able to lay it out with ease.
"I'm a little crazy. I would like them to play fast, even at the cost of a mental error," he said. "I don't like to see hesitation on the field, so even if you're unsure, make a decision and go and let us coach. Let us do our job, but I don't want any slow blinkers out there."
It helps he's already gained the trust of many of the players over his last three seasons in Las Vegas.
"He's going to do it his way," Maxx Crosby said. "And guys respect that because they know how hard he works and how much he loves and cares about this team and the players, and you can really feel that. You can't fake that energy, and I think that's a big reason why he got the job. ... He just has a really unique and special way of being able to relate to the players and guys feed off that energy."
"He's exactly who he is and who he says he is," Crosby added, "and I think that's really special when you have that coming from coaches."
"I've always been impressed with him as a coach," said safety Jeremy Chinn, "but for him taking a bigger leadership role, he's definitely embraced it. He's really allowed this defense to be not necessarily just his defense, but our defense, in a sense. So, that's a good feeling for the players."
Leonard understands his new role will bring plenty of adjustments, yet he's fully embracing the opportunity and isn't taking the moment lightly. Becoming an NFL defensive coordinator is a milestone he's been preparing for since his early years with the Giants over a decade ago.
"I think I was terrible my first year as position coach, I really do," Leonard said candidly. "I was the outside linebackers coach at the Giants, and I just focused on evolving on that while keeping notes of what I would do. But I didn't press to climb the coaching ladder, it wasn't as important to me. I was like, 'It'll happen when it's supposed to happen, but just make sure I'm ready. ... I always felt like if I worked hard and did a good job at the job I had, it will lead to another opportunity rather than chasing something else."