I get the impression that most of the psychology of creativity has been too much focused on the problem of 'where do (good) ideas come from?'
The main idea, and indeed the only idea compatible with the non-teleological assumptions of modern biology, is some version of the mechanism of Natural Selection, for example that the creative process involves:
1. a random generation of ideas followed by
2. selection among them.
(HJ Eysenck surveys and expounds this model in his book Genius of 1995).
Broadly, the theory is that a creative person is one with high trait psychoticism/ schizotypy (or possibly Openness to Experience) has a way of thinking which is prone to more-inclusive and wide ranging associations - so instead of generating just one idea, they generate a range of ideas which are novel, but of course nearly all wrong or incoherent or in some way worse.
(The analogy is with genetic mutations, nearly all of which are deleterious.)
A creative genius is assumed to be a person who does this, but who is also able to select among these many random ideas using their extremely high intelligence to test their plausibility in terms of coherence with existing knowledge.
(The analogy is with the natural selection mechanism of reproductive success - most mutations lead to death, sterility, or reduced reproduction; but a few beneficial mutations are selected because they increase reproductive success - and 'good ideas' are selected because they first of all make sense and then do well when scientifically 'tested'.)
So, the answer to 'where do good ideas come from?' is that they are chosen from a pool of what are mostly (nearly-but-not-quite ALL) bad ideas, having been randomly generated - and the essence of genius is is to sift these bad ideas in hope that a good idea might be lurking among them.
Whether or not this is a plausible or possible way n which genius works is not really a matter for empirical study - rather it is just about the only way that genius could work, given the constraints of post-Darwinian biology and the ruling-out of their existing any external source of correct ideas, which the genius might be supposed to be accessing.
In particular, given that the standard ancient explanation of 'divine inspiration' is ruled out as an explanation of Genius, then some version of natural selection is the only alternative that humankind has come up with.
But the focus of explanation of creativity could, and perhaps should, be shifted.
Rather than focusing on 'where do good ideas come from?' it may be more useful to focus on what it is that enables - or predisposes - a person to recognize that there is a problem.
By this account a creative person is one who perceives problems that would benefit from being solved; so the special gift of a creative genius would have a lot to do with their ability to discern soluble problems. Soluble problems of such a type that - if they can be solved - would make a big difference to things.
Such a genius would not have to be better than other people at coming up with answers, just much better at knowing when and where there was a problem.
Indeed, this might be his main contribution - and having defined the problem, it might be that a lot of people are able to contribute possible solutions just as well as the genius who made it all possible.
An example would be the act of creativity involved in recognizing a new disease - recognizing that there was a pattern - drawing a line around some part of the world and revealing it as a coherent entity.
So - by this account - Michael S Gottlieb was the primary creative mind involved in the discovery of AIDS because he looked at the sea of disorders and drew a line around a particular combination of signs and symptoms - a new syndrome.
Once this had been done, the famous, over-praised (and over-rewarded) leaders of uncreative but hyper-resourced Big Lab teams could throw manpower and machines at the problem until the causal agent was discovered (which was almost inevitable, sooner or later).
So - I am suggesting that a creative person is one who has the personality, or disposition, to recognize and define problems - and not necessarily the person who is especially good at solving problems
(Because the 'creative' may not have the power and resources to solve the problem he has discovered - and anyway solving the problem may not require much creativity - nonetheless, without the creative person, there would be no problem to be solved. Creativity is primary.)