Nietzsche famously said that there are not facts, only interpretations. The claim of science is rationality, but scientist are human, and therefore limited on the capacity to perceive reality objectively. The tool used by the scientific discipline to approach objectivity is the scientific method. Science is a belief system and scientist are subject to cultural and individual biases. Yet not all belief systems are religious. In the scientific belief system the predictive power of theory is the ruling consideration. Religious belief are magical and facts or experience are secondary to dogma. A rationalization of facts is necessary to fit them in the religious model.
Atheism per se is not scientific, it might be a religion for some, yet the scientific position cannot be but agnostic. In the human experience there is not factual or theoretical proof of the existence of a supernatural sentient being. If it were, they will be only one religion and the mechanics of how to relate to the supernatural will be common knowledge.
It is hard to define anything. Words like religion are especially hard to define because they are used to mean different things depending of speaker and context. Particularly, in my personal experience most people confuse magic with religion and folk reasons for religion beliefs are actually magic thinking: Means to control or influence reality by magic.
One thing I do not agree with is the statement that religion is puzzling because there is no benefit to it. Humans need meaning and a sense of belonging: Religion is the cultural manifestation of those instinctive needs.
Humans are a singularity, but the underlying mechanisms of behavior are a product of evolution, and as such, are shared among other animals. In any case, behavioral drivers explain group behavior and individual behavior in a statistical sense, as a general patterns. Furthermore, humans are for the most part unaware of their own motivations.
A scientific explanation of human behavior has to be functional and reductionist because the scientific method is analytic and function and behavior can be observed and measure, while meaning is subjective and not directly observable.