Thibault, Michelle Ball and Jamie Garman are they guilty of espionage?

Typically this is a crime to foreign governments, however, they worked for someone or an organization.

This is not a reach and must be considered

Espionage is the crime of secretly obtaining or transmitting information without authorization for the purpose of benefiting a foreign power, organization, or entity. It involves the collection of confidential, classified, or proprietary information through spying, surveillance, or other covert means. Under 18 U.S.C. § 794.
https://www.law.cornell.edu/wex/espionage