1 Timothy 4:1 - Now the Spirit expressly says that in latter times some will depart from the faith, giving heed to deceiving spirits and doctrines of demons, 2 speaking lies in hypocrisy, having their own conscience seared with a hot iron, 3 forbidding to marry, and commanding to abstain from foods which God created to be received with thanksgiving by those who believe and know the truth.
So you presume that "depart from the faith" means that born again believers depart from saving faith in Christ and lose their salvation? The words "the faith" (Gr. tês pisteôs) in this context means the apostolic faith, the New Testament apostolic body of doctrines. Some who are in a state of professing adherence to the apostolic faith, nevertheless will in both doctrine and practice depart from it, giving heed to deceiving spirits and doctrines of demons, which demonstrates that their faith was never firmly rooted and established from the start.
Some "nominal" Christians will abandon the Christian faith, the New Testament apostolic body of doctrines for cults or false religions. That does not prove they were previously born again. In 1 John 2:19, we read - They went out from us, but they were not of us; for if they had been of us, they would have continued with us; but they went out that they might be made manifest, that none of them were of us.
I believe the beginning of such a major departing from the apostolic faith was evidenced as the Roman Catholic church rose in the early 4th century. The Roman Catholic church forbids it's clergy to marry. The Roman Catholic church has other demonic doctrines such as transubstantiation, purgatory, indulgences, papal infallibility etc..