I had a feeling about this since the moment I heard about the explosion. Maybe this information doesn't matter, but let's say that the machines that were connected to the internet. It's likely that they were connected to the same internet the county/city has.
What's interesting about this is (in Atlanta's example) their govt. website is registered through Akamai Technologies. Looked into them and found this https://www.akamai.com/us/en/about/news/press/2020-press/akamai-and-att-extend-relationship-through-2023.jsp as they have a relationship with AT&T. So what if this was an attack on their data center to erase any tracks, or something related to solar winds/dominion?
I mentioned this earlier but I found this interesting:
In PA's example, their state website is hosted through a company called Akamai Technologies, and they partner with AT&T (https://www.akamai.com/us/en/about/news/press/2020-press/akamai-and-att-extend-relationship-through-2023.jsp). CEO of Akamai Technologies: "Professor Leighton has served on numerous governmental, industrial and academic committees. From 2003-05, he served as Chair of the President's Information Technology Advisory Committee on Cyber Security." (https://math.mit.edu/directory/profile.php?pid=144)
It would make sense why their state/possibly county govts use them for their internet solutions. Perhaps the systems were maybe connected to a network that was trough Akamai and it was an attack on the data centers so they could try and destroy data?