Photos edited in Snapseed on iOS and saved via the Save or Save a copy functions are non-destructive, maintaining the ability to be re-edited at a later time. Some programs like Lightroom, Image Capture, and iPhoto cannot read this non-destructive format.
To create a file that these programs can read, choose Export when saving the image in Snapseed to create a duplicate file. This new jpeg file has the edit stack flattened and cannot be re-edited, but it can be read by any other image editing program.
Or, use a cloud sharing service like Google Drive or Dropbox to synchronize images to your desktop. The edit stack will be flattened during the upload process so that other image editing programs can read the image, but this will allow you to continue using Save or Save a copy on your device.