It turns out Mariah Carey was the one to pull the strings for Jay Z to be appointed president of Def Jam between 2004 and 2008..
In a recent interview with RapRadar, music industry mogul LA Reid revealed how he made the decision to name Jay Z president of Def Jam back in 2004. Around that time, he had just become the chairman and CEO of The Island Def Jam Music Group and he really didn’t know which route to take his new venture.
While he was trying to figure out who he could hire to help him out, he called his very good friend Mariah Carey and told her about his issue. According to LA Reid, she immediately suggested he should work with Sean Carter aka Jay Z, “Hire Jigga!”, she said. Apparently that same day, Jay Z appeared in his office a few seconds after his conversation with Carey. “I was like wait, they choreographed this,” Reid recalls. “That was too good. He was so on time and it worked out.”
LA Reid went on to say that Jay Z took his new job really seriously and attended every single meeting on time. He was also very invested in coaching and advising newly signed artists.

Jay Z, Mariah Carey and LA Reid