They're trading it for something like 3 1st round picks. This isn't necessarily a bad idea since the 1st overall pick is going to be a QB and that's the only thing the Bears DON'T actually need...
I agree with this, after all, Lamar Jackson/Jalen Hurts type qbs are typically the best bc they can develop into great passers while being good rushers. It's not like qbs like Mac Jones are suddenly gonna turn into Usain Bolt.
If we look at Justin Fields' individual performance, he's the best thing on the team right now. So if the Bears trade down (with let's say the raiders) they suddenly have two 1st's and some picks later. Then they can go after what they really need: an offensive line and a decent WR.