Cura confused as to what's touching the buildplate?
The up- or down-ness of a part is its Z-orientation, which is specified in STL. It looks like whoever published that STL file published it upside down, requiring you to flip the part or rotate it by 180. You can flip it in Cura as you've done or leave a comment to the author of the STL that the part is upside down.  However, the author may not know how to fix this because low-end modeling tools typically do not have the capability of flipping a model. In these cases, using another tool such as Cura or Slicer can generate a right-side up model. Cura seems to like generating AMF files, so I use Slicer to generate STL files for upside down models. Once you correct the STL file, you'll be able to import the model directly into Cura right-side up.