I say this just to offer evidence that something about "rationality" works.

Rationality working is one possible explanation of this, but it's not the only one or even the most likely.

There are all sorts of interesting sociological differences between actively religious people and the nonreligious, usually to the advantage of theists. They live longer, report greater happiness, are healthier by most measures of health, and I think have some protection against mental disease. Most studies investigating these advantages find they have nothing to do with the content of the religion and everything to do with the religion providing easy access to the religious community, a friendly and supportive social group to which other believers have an automatic "in".

I have a feeling this works in more subtle ways than just the obvious; it's not just about going to church and seeing people, but about slowly absorbing these people's norms (which are usually pretty positive in practice even when the theory behind them is repulsive) and internalizing their conception of you as a genuinely okay person because you're part of the in-group.

A lot of what you're talking about sounds potentially mediated by the same factors. You are part of a large and active RL community of rationalists and may have internalized the idea of fellow rationalists as your in-group, which means you're adjusting your behavior to conform to rationalist norms and values rather than the norms and values of whatever was your in-group before.

This is not to devalue the importance of the material - most of us would not fit into a religious community no matter how hard we tried and so the material deserves a lot of credit as the attractor around which a community of interesting non-religious people can form - but I think the value of the material is indirect rather than direct.