If Flew's newfound belief in God is rooted in being old and nearing death, then it would follow that Flew's atheism was rooted in the fact that he was young and unmindful of death.
The young always think they are immortal, and death (if they think of it at all) is far far away. Attitudes tend to change with age and the reality of one's mortality.
Flew gives no rational reasoning for his "conversion", no research papers, no book. He basically says, "I changed my mind", and that kind of statement can only lead to a suspicion that Flew knows he is soon to meet his maker.