Inclusion Body Disease
There isnt a great deal known about the disease or how widespread it is in Aust. Effects pythons, boas and some elapids. Thought to be viral. Incubation unknown- could be weeks could be months spread through contact with infected snake or droplets in the air. The resulting inclusion bodies can cause damage anywhere in the body (nerves, brain, spinal cord and organs) leading to death. So you were spot on with the nervous symptoms, being tremors, disorientation, lack of coordination etc. Euthanasia is the right decision as yet there is no treatment and if left the snake would waste away.
Hope that helps