Serre, recounting a discussion with Andre Weil, has said that "mathematics is not made by people with long experience, with a lot of knowledge, and so on, no. New ideas come without that."

Moreover, he has to be really interested in something. And if you are really interested in a question, and you begin reading what people have done around it, very often you discover that they have not done anything. They always talk on something else, or they made a hypothesis which is not true in your case, they have very rarely done something useful. So you reduce the literature to very little. So you have to find new ideas. But, of course, if you can find connections with something else, it helps a lot. - J.P. Serre (2003).

https://www.youtube.com/watch?v=NTZh6cuezv4&t=1612s&ab_channel=TheAbelPrize