When linking to files in Google Sheets, by default a link is created to a web page with an image on that page.
To directly link to the image itself:
- Got to the file in Google Sheets
- The link will look like this: https://docs.google.com/spreadsheets/d/FILE_ID/edit#gid=0
- Remove the 'edit#gid=0' and add 'export?format=csv'
- Your link will now look like this: https://docs.google.com/spreadsheets/d/FILE_ID/export?format=csv
That's it, this link will now directly download a CSV file