Probably for the same reason the Jets looked better under Flacco than Darnold.
Neither of these guys are particularly good QBs. Which is why their respective teams moved on from them and coaches lost their jobs in the process.
Had two meh-to-poor years. One good with a nagging injury, it was the most recent. Im not convinced either, but this is a big year for him. If he has a great season, panthers may be forced to use the tag on him. Plus with the rebound in cap space, he could easily get top 5 money on the open market if he has a great year too. The whole NFL is looking for speed and the whole league knows Djack has elite speed.