Is the falling away really happening?

John 6:64 But there are some of you who do not believe.” For Jesus knew from the beginning who they were who did not believe, and who it was who would [a]betray Him. 65 And He was saying, “For this reason I have told you that no one can come to Me unless it has been granted him from the Father.” 66 As a result of this many of His disciples left, and would no longer walk with Him. 67 So Jesus said to the twelve, “You do not want to leave also, do you?” 68 Simon Peter answered Him, “Lord, to whom shall we go? You have words of eternal life. 69 And we have already believed and have come to know that You are the Holy One of God.”

2 Thess:1 Now we ask you, brothers and sisters, regarding the coming of our Lord Jesus Christ and our gathering together to Him, 2 that you not be quickly shaken from your ]composure or be disturbed either by a spirit, or a message, or a letter as if from us, to the effect that the day of the Lord has come. 3 No one is to deceive you in any way! For it will not come unless the apostasy comes first, and the man of lawlessness is revealed, the son of destruction, 4 who opposes and exalts himself above every so-called god or object of worship, so that he takes his seat in the temple of God, displaying himself as being God. 5 Do you not remember that while I was still with you, I was telling you these things?