No, there would be no lawsuit since Google was well within their grounds to reject his purchase. From their terms of service: https://domains.google.com/tos htt

No, there would be no lawsuit since Google was well within their grounds to reject his purchase. From their terms of service: https://domains.google.com/tos https://domains.google.com/tos 3. Domain Name Availability. Google does not guarantee that Registrant will be able to register or renew a desired domain name, even if Google’s systems indicate that the domain name is available or Registrant is able to complete an order with respect to such domain name. Google cannot know with certainty whether or not a third party is simultaneously seeking to register the domain name that Registrant is seeking to register, or whether there are any inaccuracies or errors in the domain name registration or renewal process or related databases, including the various WHOIS or other Registry Operator databases. Google is not responsible for any inaccuracies or errors in the domain name registration or renewal process. 4. Registration Acceptance. Google may accept or reject Registrant’s application for registration or renewal for any reason at its sole discretion, including, rejection due to a prohibited, improper, unavailable, infringing or otherwise questionable domain name. The terms of service give Google plenty of room to reject his purchase. Not to mention it should not have been available anyway since the WHOIS for google.com expires on 14/9/2020. A case like this would be quickly kicked out of court.