Grothendieck is an interesting example of how quickly this changed [1]. If you have not heard of him, he is one of the two or three most important mathematicians of the 20th century, but his work was wildly abstract, so tends to be less well known.
He was passed over for the Fields medal in 1958 at age 30 because his advisor was on the committee, and wanted more of his work to be published to prove it wasn't favouritism. Then in 1962, he was deemed to be _too_ established for the medal, no longer an up-and-coming star. And then in 1966, the attitude of the committee changed to "the Nobel of math" and he won it!
But that "change" didn't persist. Another explanation is just that hewas an emerging talent, then he seemed to have done the thing mathematicians often do where he settled down to flesh out the brilliant ideas he'd already had, but then it became clear he was still producing innovative output!
Sorry not sure I understand you post, but if I follow:
- you're claiming that the Fields medal did not switch over in 1966 - I think many would disagree, that's generally cited as the year the change happened.
- you're claiming that a good explanation why Grothendieck didn't win in 1962 is because he was just fleshing things out? I think that is also incorrect - he introduced etale cohomology in 1960 - from 58-66 Grothendieck's output was pretty ridiculous.
He was passed over for the Fields medal in 1958 at age 30 because his advisor was on the committee, and wanted more of his work to be published to prove it wasn't favouritism. Then in 1962, he was deemed to be _too_ established for the medal, no longer an up-and-coming star. And then in 1966, the attitude of the committee changed to "the Nobel of math" and he won it!
[1] https://hsm.stackexchange.com/questions/14250/grothendieck-a...