Those are some giant-sized assumptions. I was playing about 1979 onward, for whatever that’s worth. I referenced Basic Role-Playing, which was clearly based on D&D stats with percentile skills added, and Rolemaster, which literally began as options modules for D&D before become its own system. Neither of these games had any noticeable elements of war gaming. They didn’t even have rules for map-based conflict and had completely abandoned early D&D’s usage of tabletop scale for distances.
My apologies for making too many assumptions - you are correct, and your points are well-made. I'm just a bit skeptical about the Thief-BRP/Rolemaster connection being so direct when the percentile concept was clearly bouncing around (and very widely used, oddly - more widely used than a lot of D&D-style mechanics).
When I say wargame, I'm including skirmish/squad-level games, not sure if I confused the issue by not mentioning that.
Champions did at least utilize hex maps, so I could see an argument for a wargame influence there. And perhaps building a character from points is derived from building army lists by points? It didn’t feel like a wargame, but I wouldn’t be shocked if the designers were wargamers.
Champions/HERO screams "squad-level tactics game" specifically. The entire rules-set seems like it's perfectly designed for simulating a small-ish number of troops (say, 4-12) going up against a similarly-sized squad in a 20th century combat, and using it for superheroes feels to me like an odd repurposing. It works in a sort of literal fashion, but it feels like "what if superheroes were real and engage in squad-level combat?" rather than a game actually about comic-book superheroes.
At least it's a cogent game that actually works though! Superhero 2044 is a total mess (despite being the first professionally produced RPG - Lou Zocchi clearly had more resources available than some!).
Re designers, I mean, we can look into the backgrounds of various designers of the era if you feel that would be helpful? I think it's fair to say most of them are going to have a background in playing or designing wargames, just like Gygax and Arneson (I suspect this is true of a large proportion of pre-'90s RPG designers, and a significant proportion post-'90s even).
I agree with your point that RPGs rapidly reached into communities which didn't wargame, to be clear. You can particularly see that as the '80s wears on.