I don't know WHY THE FUCK any GM would trade a first rounder for Fields at this point? He lasted until #11 when he was drafted (probably would have lasted way longer without trade ups), was the 4th QB taken in that draft, so it's not like the opinions on him were super high in the first place. Bears burned through several OCs because it's literally impossible to scheme up any kind of legit passing game with him, he is a running QB but at the same time is still a sack magnet, he confirmed every single concern and never improved at all.
So basically someone would have to think of him as highly as he was thought of coming out of college, completely ignore his trash years and inability to improve at anything. That said, it only takes one idiot desperate GM.