When I think GOAT, I think Michael Jordan, Mario Lemieux, or Tom Brady. That said, Biles is likely the greatest female gymnast to ever perform. I think when you are a GOAT, there is pressure in every step you take in life. Some can handle it for a lifetime, or at least an entire athletic career, some cannot.
The three males I named above, were able to get to the top and deal with what it took to stay there. I think Simone Biles had been comfortable as a GOAT, but, NBC and other corporates have build her up so high that the pressure caused her to just "crack". Anyone who has seen her flawless performances of the past, should know something was wrong when on the first night she didn't hit any of her routines.
I think Biles realized she couldn't handle the pressure, and did right by pulling out so the team could still get a medal. I would be surprised if she competed in any individual events. She dominated the sport for a long period of time, but, she just became overwhelmed at the wrong time. Perhaps she will come back, but, usually when a star cracks, things are never the same again.
I wish her well, it just shows you that people we see as superhuman and infallible, are in fact human, and feel alot of the same things that an average Joe would feel. Some can handle it and retire on top, some cannot.