What I'm about to say is obviously just speculation, but if it was some terms of service I was violating, or their system goofing up and believing I was a free tier account and hence them stopping everything as they needed to make space for a paid service, wouldn't my server shut down first and my account be deleted second?
If there was some problematic material found to be stored on my server, or if I was illegally running a mail-server, TOR exit node, crypto miner, illegal streaming site, or something else that was violating the TOS, wouldn't the server be the first thing they irreversibly nuke?
The server was apparently constantly running, even when my account was terminated. Its IP address and any public access (ingress, egress rules) were removed or blocked.
The current uptime is 17 days. This makes everything all the more confusing...