Religiosity is defined as: "a comprehensive sociological term used to refer to the numerous aspects of religious activity, dedication, and belief (religious doctrine)."
Sanity is defined as: "the ability to think and behave in a normal and rational manner; sound mental health." Also as "reasonable and rational behavior".
What is "normal" is determined by society and culture, not necessarily by the "majority".
Using a cell phone to communicate would be an example of "reasonable and rational behavior". But if the majority of its users text instead of talk on those phone, that does not make "texting" Normal just because of the majority of people doing it.
To me, religiosity is a social situation that requires a high amount of judgemental thought processes. And most religions start from the NEGATIVE as in, "all humans are born in sin or are imperfect in some way". The only way to be accepted (saved) to this club is to follow their rules.
Unfortunately, their rules make no sense, some of them are the outright result of insanity - people hearing voices, experiencing raptures, talking in tongues, seeing things that are not there or that no one else can see, having vivid dreams of heaven or hell, feelings of superiority, believing in magic/demons/sorcery/ghosts/reincarnations/life after death/3,000 gods.
"Normal" or logical people do not actually experience these things. They may at times, lie, and say that they do, but they can still tell the difference between reality and fantasy, which makes them sane.
Most of mankind has a social urge. A longing to "belong" to a group. This is probably an evolutionary defense mechanism as it is easier to survive in a group than it is to survive solo. Some have described this longing as a "god shaped hole".
If one can break free from group think and the insanity of religion, they discover their natural ability to survive in a crazy world. No amount of believing in a thing will make it real. You can wish and pray all you want, but grandpa isn't going to give you a hug ever again after he dies. Your beloved pets aren't going to come back to life either. And your severed legs cannot be faith healed.
Religion will not save an insane person, nor will it make a sane person religious. But the vestigial longing to join the crowd is a strong one. It has just passed its point of usefulness in today's world. We are able to survive quite well on our own now. It doesn't even matter if you are religious or not.