Alternatively, at some point a QB is going to get hurt. Remember how bad it was last year?
Bears can probably wait until somebody goes down and get fair compensation for him. It's the start of the year, everyone has leverage because all their players are healthy and they can still draft a QB.
Remember the "Passtronaut" from last season?

If I'm Chicago, I'm taking nothing less than a 3rd Rounder now or I'm taking the comp pick later. They really have no reason to rush as Fields' value is lower now than it'll be for a few months pre draft. But once people miss out on a QB and/or theirs gets hurt, suddenly Justin becomes the best option available to "save their season".
The Browns, Bengals, Jets, and Vikings would have all been interested in Fields last year after their starter went down.