In my understanding there is no explanatory power in this text: it’s not offering any explanation as to why people would hold a belief as attire rather than as cheering, anticipation-controlling or any of the other categories described. All we get is a description of or criteria for recognizing belief as attire.
This is by and large correct. The fact that people hold beliefs as attire does not say anything as to why they do so. What’s being explained is the question, “Why do people believe such-and-such things?” and the explanation is “to identify with their group.” “Why do people hold beliefs that connect them to their groups?” is a separate question, and the answer probably lies in evolutionary psychology.
This is by and large correct. The fact that people hold beliefs as attire does not say anything as to why they do so. What’s being explained is the question, “Why do people believe such-and-such things?” and the explanation is “to identify with their group.” “Why do people hold beliefs that connect them to their groups?” is a separate question, and the answer probably lies in evolutionary psychology.