Totally a CYA trade for Ernie, unless there are significant futures involved. Ariza makes them marginally better, so in the garbage East, they may be able to nab the 8th seed.
Instead of doing what they should have done in shipping Wall and Porter out for high futures, setting up their roster for future flexibility and a high pick in a very good draft, he makes sure the roster is handcuffed in luxury tax hell while sitting no better than a low playoff seed.
Maybe this is just step one, and he's leveraging LA's apparent interest in both Ariza and Wall to get a better package, but I don't think Ernie can envision more than one mediocre move at a time.