The people that watch Digital Foundry are indeed the hardcore enthusiasts, and don't make up that large a portion of the overall market. It's very inaccurate to say that they aren't nearly big enough to make a difference in the console marketplace however. They are primarily the audience that gets a console to its first 10m unit sales, and the more casual audience that buys the console later both gets their recommendations from that "one hardcore enthusiast" friend, and will generally buy the console that most of the enthusiasts bought up to this point, in order to be able to play with them.
As for 2/3 generations you cited being won by the "weaker" console, you're painting a picture without context.
The 6th generation was already decided before the OG Xbox even hit the market. That generation had effectively started off globally in 1999 with the Dreamcast. The Dreamcast is considered to have had possibly the most impressive first year lineup in console history, was dirt cheap right out of the gate and brought the initial promise of online gaming to the living room. It's momentum however was stopped dead when Sony showed a bunch of tech demos for the PS2 that looked drastically better what had been shown for the Dreamcast up to that point. On launch the PS2's software lineup was lackluster enough that The Matrix DVD movie was seen its legit killer app... but that didn't matter and it set sales records everywhere prior to the software eventually catching up.
The 7th gen is more of a Genesis/SNES situation than one console simply being superior to the other. The PS3 isn't simply "better" than than the Xbox 360, and more importantly when comparing software that exists across both platform, the PS3 was consistently coming off worse. People waving the PS3's supposed superiority could basically only cite a handful of exclusive 1st party offerings (Killzone 2, Uncharted 2, God of War 3, The Last of Us) which were being largely balanced by the graphical showcases the 360 itself had (Project Gotham 4, Halo 4, Gears of War 3, Forza Horizon), but then you had face-offs between the majority of multiplats reading similarly to how the XB1 did against the PS4 in such games. For all intents and purposes the 360 served that generation as the more powerful console of the two, despite being out the year before. It was absolutely not a good look for PlayStation that generation in terms of power. If the PS3 had been running those "same third party games you could play elsewhere" noticeably better, rather than the 360 doing that, the PS3 would have done way, way better in the 360's key markets.
So yes, power is important to a console's fate... it just won't magically erase all other market conditions like launching into a market where the opponent is already past the hardcore market sales and snowballing sales as the defacto console for the generation. And price also isn't a sure win, because when the PS2 hit you could have basically bought 2 Dreamcast for 1 PS2, but the PS2 slaughtered it effortlessly based primarily on promises of superior performance.
