” ‘Invasion of the Body Snatchers’ may well have been better in its original version before the studio interfered. … also had the opening and ending sequences … inserted to ensure a relatively ‘happy ending’. “
The studio revised version was closer to the original book. The producer and/or director had insisted on setting the ending where the aliens look like they are going to win (and in the terrible remake, have won). In the original story, the aliens, frustrated by the humans’s resistance (of which, we are told, the adventures of the protagonist were only a part), and having satisfied part of their goal by reproducing, take off and abandon Earth, leaving behind the humans they had taken over as mere mindless shells. Rumor has it that the studio ordered the changes and the opening and closing scenes which frame the film narrative, because they didn’t like the dark ending and thought audiences wouldn’t either. But it is possible that the author objected to the changes the screenwriter made as well. Some SF writers had more influence with the Hollywood establishment than others. I know that is hard to believe when you have to watch the butchered and botched versions of SF classics Like “Starship Troopers” and “Nightfall,” but it was true from time to time.