I got better results:

Input (original) name: the-northern-trifid-nebula-8499-1920x1200.jpg type: image/jpeg size: 737.26 KB

Output (compressed) name: the-northern-trifid-nebula-8499-1920x1200.jpg type: image/jpeg size: 263.17 KB (64.30% off)

I guess your original was more optimised than mine.

A tool like this should definitely check to make sure it has actually reduced the file size and, if not, just return the original with a note that it couldn't make any gains.