Artists whose careers diminished due to a lack of ambition?

Of course, not every artist has to aspire to lasting worldwide superstardom to be successful or beloved. However, there are a select few artists whose prospects dried up due to a lack of musical ambition or consistent output, and their inability to strive for more becomes annoying rather than charming. Even many Trainwreckords were by artists who failed at a notable project (not that they succeeded).

This comes to mind in the One Hit Wonderland episode, The Night Chicago Died. Paper Lace was a kitschy 1970s rock band lacking a distinct identity that lucked out with "Billy Don't Be a Hero" and "The Night Chicago Died." They failed to expand upon their sound, unsuccessfully tried to break their contract with their record label, unceremoniously disbanded in the 1980s, and reformed as two zombie bands that are still active today, yet they never released any major follow-up albums or singles. Todd commented, "They seem like men with very limited ambitions. They liked having hits but they wanted to be [you know] Three Dog Night, not The Beatles."

Are there similar artists who come to mind for you? I'm curious to hear people's thoughts.