I am wondering about what I call a latency period. In other words, Mormons who leave the church become deists, agnostics, or atheists for a number of years, disillusioned with all religions, and later realize that there are other, better religions. Direct conversion from Mormonism to Catholicism probably isn’t all that frequent, and might result in people becoming “Mormo-Catholic.”
As for BoM criticism techniques being applied to the Bible, influencing people to toss the Bible, that is specious reasoning. The Bible is undeniably an ancient text. Part of the BoM was originally written as a parody of the Bible. Both the Bible and the BoM can be read with sensitivity to allegory. We Catholics interpret many passages in the Bible as being both allegory and literal truth, as logic and reason dictate-- no problem. Few Mormons convert to Biblical fundamentalist churches-- although some from jack-Mormon families drift into such churches for obvious reasons. Finally, because the BoM is based on the Bible, the best of that book condemns Mormonism.