Why didn't she go on to bigger things?
Multiple reasons, including:share
A lack of success in the films after Manhattan - In what has to be a sign that acting was not her “forte”, Hemingway managed to star in numerous films which either bombed or under-performed to the point where they were virtual “bombs”. None of her starring, nor her supporting roles, were in films that made any money and her career sagged as a result.
Personal Best - The early 1980s had a number of “gay-themed” films, including this one. Not only did it bomb at the box office, it started rumors of Hemingway being a lesbian which lasted for decades. Since she wasn’t and she was seeking roles in films that were looking to cast a straight female actor, things for her career went poorly.
Star 80 - The biopic of murdered Playboy model Dorothy Stratten ironically made her costar, a then-unknown Eric Roberts into a star while doing very little for Hemingway. Since the film was also a financial bomb, Hemingway’s career stalled and it was two years until her next feature film role.
Her height - At six feet tall, Hemingway towers over the majority of actors in Hollywood. Since she unfortunately didn’t have the range of tall female actors like Geena Davis, Laura Dern, or Sigourney Weaver, it was less compelling to cast her in roles. Coupled with her lack of box office success, she quickly became eclipsed by other female actors.
Her issues with substance abuse and mental illness - Hemingway has experienced a number personal issues involving substance and mental illness. This problems worsened as she grew older and they almost certainly prevented her from accepting roles that would have raised her profile and perhaps even allowed some of he projects to succeed financially.
Manhattan really should have been the start of a promising career for Mariel Hemingway.
Unfortunately a number of personal and health-related issues conspired to make her an answer for a “Whatever happened to….?” question, rather than a successful performer.