If you were killed trying to dock in Jita, that’s because you weren’t docking.
You likely warp straight to the station and stopped paying attention, thinking you were safe. However, when you initiate a warp to a stration, there will be times when you don’t land perfectly within Docking radius, but a couple of kilometer out. In those instances, your ship is will become targettable during the short time you slowly move towards the station, making you vulnerable to getting killed like this.
The solution is to create an “Insta dock bookmark”. This is simply just a bookmark that is well within the docking radius of the station that you warp to, so that as soon you as land out of warp, you are guaranteed to be within Docking radius, and can immediately dock without opening yourself up to vulnerability.
Try that next time.
And to answer your question, no, they’re not robots. They’re just there looking for easy kills and ganks from bad players who aren’t paying attention and don’t use insta-dock bookmarks.
They can “come back online so quickly” because nothing is stopping them from doing so. If you think reporting a ganker in Jita means they get banned or suspended, that is not the case. Ganking players is a natural part of EVE Online, but don’t worry, it only happens to bad, lazy, or otherwise poor players who don’t pay attention. You can learn to improve your gameplay so that you don’t get ganked like this.