well, I'm going to ignore the expert tag but in the end I don't believe there's a thought process there that one could identify with any actual truth.
You could say that the Panthers simply thought he was the best player, hands down. I certainly do hope that's the case.
You could say he wasn't standing out, but that fan perception and/or past mistakes like Holliday over Peter pushed him beyond.
You could say that they simply couldn't get the trade down they wanted. You could say they opened negotiations to force a trade.
You could even say that they had character concerns about Peppers and in an effort to dissuade those thoughts, they decided to open contract talks with him in a hope of seeing him under duress, that they were looking for him to make an outrageous demand to match some of the rumored remarks that may or may not have happened.
I dunno. Can't say anything for sure, till tomorrow. But hopefully they made the pick at 2 without expecting that something would be there at 34. With Rumph and Sheppard expecting to be gone, IMO the CB depth is no better than DE depth, especially with Ross having so many concerns.