From my observation of what you have described, it sounds like he always had loose boundaries and decided to not push the improvement of your mental health in place of just giving you what you wanted, which was more of a friend relationship. He probably saw you as an easy session each week. Being a friend and going for walks was probably a nice break for him. That being said I am sure he had some positive feelings from the relationship. It doesn't sound like he was too devoted to his profession or regretted his decisions.

I am sure he knew what he was doing was wrong and that it was unethical to continue to "treat" you (provide therapy) in this manner. It also sounds like he has been wanting out of the profession for awhile now and he was probably just going through the motions for some time. Now that he found another job and knows he moving on, I'm sure he is relieved and is just biding his time. He has moved on mentally. Only he knows the truth but maybe he feels that treating you coldly will help you get over him. He probably has come to terms with the fact that he should have been acting like a therapist all along and he wants you to know that he can't be your friend.

I am sorry that you are going through this and that he allowed it to go on for so long in this manner.