Anti vaccine rhetoric has an extremely high correlation to religious people. The commentor was speculating about how these people in the past would have felt about the anti vaccine people today. It’s a valid question. People back then didn’t have access to information or access to much real hope; it’s not surprising they were religious.
You sound like an attentive cat carer. Cat was lucky to have you. The point of all this is different for everyone, but cats are a big part of the point for me. Maybe for you, you can give more cats a good life as well. When you’re ready of course, you may need time to grieve.