It is an open secret if you talk to any Google employee that Gmail data is heavily used to enrich other Google services, including ad placement, even if indirectly. They also can and will give it to authorities thanks to bulk keyword sharing agreements with or without individual warrants.
Google is not a charity. They are not giving you gmail without charge without somehow generating profit from your data. You do not need an insider leak to work that much out.
Google Workspace makes money from Gmail by charging business users for it. Gmail is the freemium version to make employees demand their employers buy Workspace over Office 365.
https://www.forbes.com/sites/thomasbrewster/2021/10/04/googl...
US citizens should take careful note of the fact their data is only usefully constitutionally protected if it is hosted at home.