Topaz was inspired by real events and people. The Soviet defector was modeled on Anatoli Golitsyn, Castro really visited Harlem, there was a French spy scandal, etc. The problems perceived in the movie stem from the incompatibility of theatrical/movie narrative with real life. The script did not cast aside the facts willy nilly in pursuit of a conventionally shaped tale. Nor did it find its own way to tell a true story, not least because it was controversial, potentially libelous, I suppose. Hitchcock was just the director, he couldn't replace what wasn't on the page.