First, I don't think most fundamental churches
can study their deconverts without concluding their deconverts' minds and souls have been taken by the devil and the only way to fight that is to go out and make more converts. They are disposed to supernatural explanations already and we already know a major theme in most such churches is that anything "bad," like deconversion, hurricanes and Democrats, is Satan's work.
Second, even if some
progressive science-minded church were to make such a study, what are they going to do with the information? Change their core beliefs? Renounce creationism, the rapture, the literal bible, papal infallibility, the trinity, whatever their study shows as major causes in deconversion?
What I would expect in this progressive case is an increase in emotional appeals and mis-information campaigns targeted to overcome deconversion thinking.
Finally, I'm not sure we should be giving advice of things that may strengthen a religious community. Humanity has suffered enough under the yoke of false belief. But to now package it, make it pretty as a result of focus-group marketing schemes, will make lifting that yoke that much harder.
Edited by AZPaul3, : consistent metaphor.