Nagging thought about Lee Harvey Oswald

All the files on the JFK assassination released a few days ago have now been trawled through, pored over and examined by journalists and conspiracy lovers. Nothing really emerged that could honestly be described as a revelation. As I blogged before, Lee Harvey Oswald did it and that's that. But there remains one little aspect of Oswald's life that still bothers me. The nagging thought won't go away. Why, after living in the Soviet Union for three years, after telling the Russians he wanted to defect, after making it clear he loved everything about the Soviet Union (until he had lived in Minsk for a couple of years), did the American embassy in Moscow give him a new passport and allow him to return to live in the US with his wife and young daughter? Why did the US immigration people at the airport where he arrived back from the Soviet Union not take him to one side, put him into one of those little rooms and grill him to death? Why didn't the FBI swoop to the airport and take him away and interrogate him? Why didn't the CIA tell the FBI that Oswald was a potential Russian agent, even if he wasn't? Did the CIA station in Moscow keep an eye on the former US Marine and did the CIA head of station ever think to himself: "This nutty guy Oswald might just turn out to be a real baddie?" Is there a super secret CIA file on Oswald and if so, is it one of the 300 documents that Trump allowed to remain classified? That's a lot of questions. But it seems absolutely extraordinary that Lee Harvey Oswald was allowed to enter the US after three years in the Soviet Union, and just carry on his life in Dallas as if he was a perfectly ok citizen. Totally bizarre. Think of today. Trump doesn't want anyone to enter the US unless they have been questioned, scanned, body-searched etc. I know it's a different era and I know Oswald had an American passport, so he wasn't an alien. But IF the FBI/CIA/Immigration Service had stopped Oswald walking through passport control and taken the trouble to investigate him thoroughly, PERHAPS the young, charismatic, inspirational John F Kennedy would not have been assassinated on November 22, 1963.