I just started a Makedonian campaign and Pyrrhus moved, he move his entire Greece force to Dalminion and then they all sat there until I conquered everything.
There is no way to alter the AI's focus or behavior. They love going after rebels, it is just hardcoded in.
I had a theory that they were going after "Rome" with their constant northward expansion (since the hardcoded "Rome" is the island in the Baltic). But that wasn't very likely given many other, better explainations (Zebras). I was going to test the stupid theory but got sidetracked by a shiny object.

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