Here you go, all Tor exit nodes:
https://check.torproject.org/exit-addresses
The Tor project does a lot of work to make operating an exit node safer and less likely to prompt the authorities to intervene. This is good, because even if the authorities did want to talk to exit node providers, those people _couldn't_ provide any useful logs.
Although they could be made to run a packet sniffer, which could provide useful information.
But the traffic between nodes is encrypted. All they may get is the previous node's IP address....then they have to start over. Go find that node operator and get them to do the same.
But most Tor users, especially the ones who are using it for disgusting purposes don't run an exit node, so I don't think I understand your point? In addition, Tor exit node IPs are basically public info already.
The exit node IP is run by an unrelated third party. Unless they're logging all of the traffic going through the exit node they have an extremely limited idea of what the exit node is doing.
The exit node IP is not totally useless. It's enough to prompt a knock on your door by the authorities. Granted, once they recognize you're running an exit node there's nothing they can do (otherwise Charter could also be held liable) but still, it can prompt an action by the authorities.
My guess that they some were researchers: at least one came from a university IP address while others were very bare-bone machines with minimal running services, possibly virtual machines or test boxes.