It's always easier to judge in hindsight. I could give biographical, philosophical, social (my fellow believers), and emotional reasons for why I believed & for why I stopped believing. When I look back now, I find so many reasons when asked to discount faith that I now think that my lack of faith is overdetermined.
There are no "incorrect motives." Taken at face value that is a recipe for misery and neurotic repressive self-deception.
As far as "Christian motives" mostly I infer from the behavior of Christians. If someone acts fearful, uncertain of themselves, or seem to believe they are so awful and their God is so wonderful & great, then certain things can be inferred. Especially, when a Christian tries to discount any discussion of motives & mental health, by asserting however forcefully that the Truth of their Beliefs make discussion of mental health, motives, etc. moot.
Seldom do Christians realize that arguments for conversion based on Hell, God's Omnipotence, and the like, have a disturbing analogy: Following Hitler so as not to go to Auschwitz.
How can any Christian be certain that they love God for His beauty, His Goodness, etc. and not because of fear of damnation? My own suspicion is that God's power makes love impossible. And don't give me any nonsense about the Cross. Jesus is still 1/3 God. He still has 1/3 of omnipotence. And if Judgment Day is to be taken seriously, how can anyone love their judge? Inequality of power precludes love. Love is between equals.
Where there is inequality power then one should talk of pity.
The motivations of Christians, until shown otherwise are fear, self-disgust, and anger. That most Christians experience their motivations as "love" is at best evidence of the uncanny power of self-deception and wishful thinking. But that's what happens when Christ-talk is translated into everyday language.
Oh, last bit of ramble. It was George Orwell who gave me to understand that language can either reveal or it can conceal. When it conceals, it is a tool of tyranny, repression, and oppression. Language used primarily to hide truth diminishes human beings. There is an omnipresent fear of saying the secrets everybody knows, but nobody will say.