Yes, you can have your speculations about different people in the scriptures and whether or not they truly got saved and then later went to hell. However, the scriptures never once specifically tell us that a particular individual got born again and justified and then later ended up in hell. That is simply your interpretation. (and not a very good one)
However the Bible does specifically tell us that a person who is given salvation and eternal life cannot lose it. Speaking of his Sheep Jesus said "I give them eternal life and they shall never perish, neither shall anyone snatch them out of my hand. My Father, who has given them to Me, is greater than all; and no one is able to snatch them out of My Father's hand. I and My Father are one." (John 10:28)
So the Sheep are completely secure in the strong grip of the Father and the Son. Not even the Devil can snatch the sheep from the Father's omnipotent grip because, as Jesus says, the Father is greater than all. If He is greater than ALL then He is greater than the Devil.
Now you might argue that the Shepherd will not let go of the sheep but that the sheep might let go of the Shepherd. However, sheep have hooves. Since sheep have hooves, sheep cannot hold on to a shepherd anyway. It all depends on how great the Shepherd and His Father's grip is.
Besides, a sheep would not let go of the Shepherd unless he was tempted to do so. So he would only let go if the Tempter (the Devil) tempted him to do so. Yet if the Devil did tempt the sheep to let go of the Shepherd, and his temptation succeeded, then that means that the Devil would be successful in snatching the sheep out of the Father's hand. Yet Jesus specifically says no one can snatch the sheep out of the Father's hand. That that cannot happen.
Maybe you incorrectly think that a sheep is strong enough to snatch himself out of the Father's omnipotent grip. That is silly. How strong is a sheep compared to God? Would an earthly Father allow a child to jerk away from his grip and run in front of a car? We take responsibility for our children's safety by holding tightly onto them. We do not let a foolish child overcome our grip and die.
Also Jesus plainly says... "I give them eternal life, and they shall never perish."
So if the sheep have eternal life and can never perish... then how does it make sense to say that some of the sheep later perish and had life that did not last for eternity because it was lost? In that case, the sheep did indeed perish and did not have eternal life. They had temporary life. And they perished. So is Jesus a liar?
Indeed, those who deny eternal security unintentionally teach that Jesus lies.
Also Jesus said..." This is the will of the Father who sent Me, that of all He has given Me I should lose nothing, but should raise it up at the last day." John 6:39
So the Father has given His Son, the great Shepherd, some sheep. And the Son specifically tells us that the Father's will for the Son is that the Son lose NONE of those given to Him. Later Jesus says " I always do those things that please Him (the Father) John 8:29 So God's will is that the Son lose no sheep and the Son says that He ALWAYS does the things that please the Father.
Jesus does not place the responsibility of maintaining eternal life on the sheep. He clearly says that the Father has placed that responsibility on the Son and His will is that the SON not lose any. Plus, the Father holds the sheep too, and no one ( not us or even Satan ) is stronger than the Father.
Finally, In John 5;24 Jesus says "He who hears My word and believes in Him who sent Me HAS everlasting life, and SHALL NOT come into judgment, but HAS passed from death into life."
The believer HAS (already possesses) everlasting life. (not temporal life or probationary life) And SHALL NOT come into judgment. SHALL NOT.
Jesus does not say... "Whoever believes in Me has eternal life unless he doesn't have eternal life because he goofs up... and he absolutely SHALL NOT come into judgment unless he does come into judgment because he messes up."
Of course, that is exactly the type of assurance He would have given to us if those who deny eternal security were teaching the truth. Thank God Jesus didn't learn his theology from teachers and Job's counsellors and comforters like that.