How can we reconcile God’s leading astray of disbelievers and those who have gone astray, as He says: "And he whom Allah leaves to stray—there is no guide for him," with some of them returning to faith after long deviation?

The verse, "And Allah guides not the wrongdoing people," is said to mean that Allah does not guide them as long as they persist in disbelief and wrongdoing. However, if they strive and intend to return, Allah will grant them success, as indicated by His saying, "And those who strive for Us – We will surely guide them to Our ways." It is also said that the verse refers to those whose hearts Allah has sealed, knowing that they will die as disbelievers. As for what is mentioned in the Sunnah, it confirms that a person may live in disbelief and then die as a believer, and vice versa, as in the hadith: "Indeed, one of you may perform the deeds of the people of Paradise... then the decree overtakes him, and he performs the deeds of the people of the Fire, so he enters it. And indeed, one of you may perform the deeds of the people of the Fire... then the decree overtakes him, and he performs the deeds of the people of Paradise, so he enters it." The example mentioned in the question about (Antony Flew) is incorrect; he did not embrace Islam, but rather converted to Deism, which believes in a creator God who does not intervene in human affairs, does not send messengers, does not reveal books, and does not believe in the afterlife.