Cover Art from Discogs doesn't show in Pioneer car stereo

The "bad" picture has been saved as "progressive" picture with several cycles to get its final sharpness.
The "good" picture has the property "baseline" so it is displayed in one go.

I wonder how you opened and resaved it - with a graphics editor? Then it could be that the editor had the setting to save the file as baseline file.
Apparently, the player can only cope with baseline files.

See also here:

or even here:

(the supplied files had both RGB, no CMYK)