Google and Amazon seem to be different results, as there is only one author on Google and two on Amazon.
IMHO when Calibre finds optimal matching, it merges all information into one large entry.
Note the "See at" entry on the right side of your screenshots:
- When found it on Google, we see that it's Google.
- When found it on Amazon, we see that it's Amazon.
- When found in Goodreads, we can see that all information has been merged.
See hint for the main options when fetching metadata.