Dick was a fan of comics at young age, reveling in the escapism it provided from the strict boarding school he was enrolled in. He was a big fan of Captain Marvel in particular. That fandom held with him and, years later, when he and his wife Pat began a science fiction fanzine in 1960 called Xero, Dick penned a remembrance/biography of the original Captain Marvel. The two first distributed it at that year's World Science Fiction Convention in Pittsburg and, in what was an unintentional bit genius marketing, Dick and Pat attended the show in Marvel Family costumes. The sight of the only two superheroes amid a host science fiction related costumes caused a bit of a stir and even thought the costumes were not of great quality (Dick recognized that even back then) that the embodied these favorite, almost but not quite forgotten heroes of everyone's youth and other fans came flocking to talk to the duo. Which obviously made for an easy way to introduce people to their new fanzine!
Don and Maggie Thompson were at that same convention. They evidently did not see Xero or meet the Lupoffs, that's where they had the idea to create their first fanzine focused strictly on comics: Comic Art. I suspect that it was the talk sparked by the Lupoffs spread beyond the Marvel Family to other comics that these sci-fi fans used to read, and that spread throughout the convention. (The show's attendence totalled 568 -- it wouldn't take long for a single topic to circulate.) And I further suspect that it was that general buzz that prompted the Thompsons to start Comic Art.
Xero and Comic Art landed on the desk of DC editor Julie Schwartz, himself a former fanzine publisher. So when Jerry Bails began contacting Schwartz about starting a JLA newsletter (Bails was an old fan of the JSA and this new revival greatly interested him), Schwartz passed along some of these new fanzines he had seen as examples of what was being done. Bails and Roy Thomas (who had been corresponding already) changed their approach to this JLA newsletter, broadening the scope into what became Alter-ego in 1961.
The floodgates opened, and there were soon a bevy of comics related fanzines available. The number of titles seemed to double almost every year throughout the 1960s, with prozines starting to pop up in the latter half of the decade.
For as huge a force as Bails and the Thompsons were, the Lupoffs were there at the start and (seemingly unintentionally) helped kickstart everything. There's a very direct through-line of organized fandom that goes from the Lupoffs to everything you know as fandom today.