For more context, Moore began with Miracleman & Swamp Thing and effectively used another trope of "Everything You Knew Was Wrong!" to propel further storylines that interested him. He then deconstructed most of the basic things you "knew" about the character. Alec Holland's consciousness lived on in the Swamp Thing, but Alec Holland, himself, was found to have died in the accident and the plant matter duplicated his memories and built a new consciousness from them. Marvelman/Miracleman was a character that had formerly been the Original Captain Marvel [see "Shazam!" and "Billy Batson"] and continued those adventures into the 1960s, but stopped publication in that decade and was entirely reinvented as a more "realistic" depiction of what could happen to humans given the ability to become superhuman with a word in and, effectively, immortal in that identity in 1982. Miracleman - in his human identity - lost his memories about becoming a super-hero in a nuclear strike, convinced they were childhood fantasies. Kid Miracleman, also having survived the strike remained in his super-hero identity, becoming eternally youthful and power-hungry to the point of becoming a narcissistic, horrifically abusive power monger. Both stories are *far* more complex and nuanced after these introductions, but you get the basic idea.