So called "success" can be measured in a lot of ways. Just an example, some people could say that Norman Rockwell was a great success and it also could be argued that he was stuck in a rut and produced the same stuff for years with no obvious growth.
Maybe he was happy with what he created, and the money that poured in, or maybe he got bored, but due to his success stayed in his "rut". We don't know, and it's really none of our business.
In any artistic pursuit, and the nature of the "artist" we are seldom happy with what we create. At first maybe we are thrilled but we soon find it boring and want to venture out into other areas. But perhaps financial success begins to govern our judgement.
In Ricky Nelson's Garden Party he writes about he moved on to different songs than his audience wanted to hear, because they loved his old stuff. He was booed by the audience and lost commercial success due to this. Same with Bobby Darrin.
So while to the outside world you may look like you went off the rails, in fact you may be just experimenting to move forwards in your artistic pursuits and the rest of the world doesn't get it. You may be perfectly happy with less financial success but more artistic "success" and may never reach the same level of financial success again. But that does not make you a failure.