The whole shabang about aliens and ufos have sort of died down now but was once a popular topic in the 1980s. This is partly due to the fact that nothing of any major importance has happened due to such reported events. Also a number of hoaxs were discovered concerning crop circles and faked photos of Flying Saucers. So the X files went to reruns.
One big turning point that people lost interest was due to cults that popped up. Such as the Heaven's Gate cult where they all killed their selves, and that other cult where they want to clone people because some alien told them to do it. It got too wack-o for the average person to want to be connected to this as a believer.
CNN - One year later, Heaven's Gate suicide leaves only faint trail - March 25, 1998