The probable answer is actually exceptionally simple.
The security of any network of devices is the security of its LEAST secure element. That should be somewhat intuitive.
And how did they get there?
The absolute simplest explanation is that HRC et al use Microsoft Outlook or something or other which seeks to “sync everything up”.
1: Drop the security of the main server (they even had SST disabled for a period of time!)
2: Check email from home. Computer slow? Go eat something while it syncs up. Bam, 650K emails.
Done.
“...use Microsoft Outlook or something or other which seeks to “sync everything up””
Commiecast, Google etc all want to sync-up every device I’ve got, I’ve noticed, for the past couple of years. I always answer “NO”, since all I have is a desktop, lapper, dumbphone and am still on a cable, no WiFi crap.