I’m thinking a major component was skill at manipulating smaller, normative concepts and structures, in complex ways. With practice, one can imagine more and more simultaneous pointers with ease. Memory competitions for other knowledgesets show that anybody can learn to hold many items in their mind at once, with practice.
Another part is how it is useful to use things like pointers and for loops. There are also various transforms one can perform on structures and algorithms, to mutate them into something with different properties of speed, storage use, and other forms of complexity.
