Denver would love to get off Nnaji's contract. The Nuggets also need some ball-handling/guard play off the bench. Perhaps most importantly, this trade gets Denver just below the tax line which I think they will prioritize this year.
Chicago could get some assets for taking on Nnaji's contract. How many assets is dependent on how he performs this year, but I think a second round pick is pretty fair. Now that Nnaji has another traditional center to play next to off the bench, I think we could really see him come into his own. Personally, I think Zeke Nnaji has been miscast as a center for the vast majority of his minutes in Denver. Plus, Nnaji has only ever been given minutes in a high pressure context on a contending team where he'd be pulled for any small mistakes and didn't get consistent minutes. He's still young enough that he could be a reclamation project as a highly versatile big with shooting potential.