I don’t understand the hate. His résumé is quite astounding.
He's leaving God.
Look what happened when Lucifer left God in the Christian faith.
Edit: since 2 people seemed to have missed the intended point- thinking I'm confused about Iovine leaving vs. Lucifer getting "fired", the example revolves around the implication of Lucifer as "right hand man" or "the favorite" among the angels of heaven. Then, he leaves and becomes the most hated of the hated. Conceptually, there would have been a historical time when Lucifer was as beloved as any other player in that cast- perhaps moreso- as the apparent favorite. And then, he took actions that led to his departure- whether voluntary or involuntary doesn't really matter here.
It's not about the differences in how either character left but it's an analogy for "understanding the hate." In other words, Iovine was relatively (public sentiment) fine while he was a part of Apple, but now that he's leaving, the hate wells... as if it's some defection or like he's calling our own baby ugly or something. The astounding resume doesn't matter. He's daring to choose to leave God... 'er, I mean, Apple.
Other examples of this can be found in Apple history. Remember Ron Johnson, head of Apple retail? Fine while we was within the bubble but then the crowd turned on him when he departed. His replacement was relatively welcomed until Apple realized that was not a great match, let it become known and then the crowd turned on him too going out the door and after he was gone.
Less (directly) relevant but still somewhat telling: recall when Woz said he favored an Android phone over an Apple iPhone. Woz's resume has to cast him as either the mother or father of Apple Inc. There probably is no Apple without Woz, so certainly he can have a little slack with his personal opinions. Absolutely not! This crowd ripped into him for daring to have a personal opinion that differed from the one he- and all people everywhere- should have.
When Apple acquired Beats, Iovine is one of the main points of rationalizing that $3B purchase. He was praised as music industry genius/god as this crowd tried to help sell why Apple spent that money on Beats instead of many other possibilities. Now he's leaving and "we" are quick to turn on him.
Maybe spelling it out will help the OP "understand the hate" in spite of the "astounding resume?" and "our" generally positive opinions of him in the past. Basically there is no logic in the hate- it's just the usual: How dare this man leave Apple?.. resulting in a quick turn of sentiment against him only because he's leaving. Business as usual.