If your stepfather is a good dude, talk to him and be supportive while he’s going through this. I had an almost identical situation, and he said it meant a lot to him that I called him to check in on him. My mom left him because he was fired from his job as an executive, and he just kind of gave up on looking for work. He ended up going blind a few years later.

My mom was married to her 5th husband for almost 20 years. He was a good guy until he got radicalized by a TV channel. My mom moved in with us for 3 years, and she lives with my brother in TX now. She’s MUCH better off.