It's hard to overestimate how big of a star Shirley Temple was at the height of her career. She was the top box office star for four straight years (1935-38), and was in the top ten in 1934 and 1939. Although 20th Century-Fox stars always seemed to earn more money than their meager talents deserved (see, e.g., Alice Faye, Sonja Henie), Temple was extremely good at what she did, and a real industry pro. As one story has it
[Adolphe] Menjou was having trouble on the set [of Little Miss Marker] one day with one of his lines. At the prompting of a few crew members, Shirley asked director Alexander Hall, "Is it too late to replace Mr. Menjou on this picture?"
She debuted in movies at the age of four, was an international star at the ripe old age of six, and largely washed up by the time she reached thirteen. Nevertheless, she showed her acting abilities hadn't diminished when she revived her career in the 1940s with movies like The Bachelor and the Bobby-Soxer
. She probably could have transitioned into more mature roles, but she couldn't shake her juvenile image and, I think, she just got tired of Hollywood, not unlike other child stars such as Deanna Durbin.