This idea that the evil corporations are conspiring to make people fat is just typical anti-corporate conspiratorial thinking.
Nobody floated that strawman except you.
Yeah, I've never heard that one actually put forth. They're conspiring to make money, which is what corporations do. If they knew they'd pull in twice the profit by having low calorie veggie burgers instead, they'd do it in a heartbeat. It's about the money.
My concern is when they violate laws as a "business decision" (when the risk is lower) to make that money, which corporations do frequently. But I see no back-room conspiracies going on with McDonalds.