It's just a question of ends justifying means. The average person would prefer to look better nekkid, perform better on the court/field, work fewer hours, live longer, make more money... i.e. not very specialized. Prof. X indicated it was cyclical, I believe this one is more permanent. He's right that bigger muscles are generally stronger, but the spoiler is that there is a point of diminishing returns.
To be the absolute biggest isn't easy, is very specialized (not so much in ability, but time and resources), and there's very little relative payoff (pro or amateur). To be better in a variety of activities provides you with a variety of payoffs, in a variety of magnitudes, that is very general but customizable to the individual. Classical bodybuilding can't compete IMO.
Also, stringency and nomenclature are issues; you say "athletic performance" vs. bodybuilding. I'd say bodybuilders vs. MMA fighters is roughly equal. I'd say bb vs. strongmen is roughly equal. But bb purists vs. MMA enthusiasts or bb purists vs. MMA and Strongman enthusiasts? No contest.
Lastly, as a "bb purist" or "competitor" (or strongman competitor, or MMA fighter...), at some point you can "grow out of T-Nation". At some point, you learn what works best for you and your goals, once you've learned that, T-Nation becomes a distraction or takes on a different function in your life. As a bb, if it doesn't build lean mass, you don't need to look at it. As a MMA, lean mass, total mass, quickness speed, agility,... as a strongman same (or similar) things. Not only more reasons to train certain ways, but more reason to pay attention to T-Nation as well.