Campbell was the highest rated guy on their board at #18. Why take a player you've rated lower at that pick and run the risk of your higher rated guy not being there the next time you're up? Weird things happen in drafts. Just because Mel Kiper thinks JC would've been there at a later pick doesn't mean he would have.
By all accounts there was no risk. That office made the two worst, biggest headscratching picks of the night. Some thought McDonald was a reach but he was routinely talked about as a first rounder and it's plausible, if not likely, the Jets needed to take him somewhere close to where they did in order to get him. But these picks? When you are making two universally panned picks it suggests your front office/scouting department is incompetent. At the very least they don't understand how to use/manage their draft capital to get what they want...and get the most out of it.