Many ways people implement that E2EE email service, is smoke and mirrors that still puts your data on to foreign servers – and if it touches/remains in a cloud space, even encrypted, I’d say there’s still the opportunity for the leak to occur (encryption algorithms require updates periodically for very good reason!). However, back around the time period this stuff was happening, I imagine that if they’d used a properly setup E2EE service that they controlled, the comms would not have leaked in this volume. Like it used to be common for even smaller/medium sized businesses to maintain their own Email and Blackberry messaging service servers in the 2005-2015 period, which kept comms internal to the company (barring hackers of course).

If they had that setup properly and with retention periods set for things like backups / old messages and so on, this sort of leak, I imagine, would not have happened.

IT Operations type roles in companies are less common these days, as most just dump things into the cloud (and options like BB went poof!), but there is a reason that such departments exist, and why some industries place a high premium on things like data retention (and getting rid of data when you legally can, to minimize this very sort of risk). Most of the people involved in these scandals, appear to be incredibly wealthy / business people etc – I mean, Bill Gates should’ve known for sure that this shit was highly leakable.