Is this really the case though? All shareholders are pushing for higher returns because of inflation, it's not an indication of collusion, it's an indication that the market conditions have changed.
As I said on the flip side the fact that all workers are pushing for higher salaries isn't a reflection of collusion between different sets of workers, it's just a reflection of the new economic conditions on the ground.
Shareholders are always pushing for higher returns, inflation or not. The thing is that normally Pepsi and Coke would be preventing each other from raising margins. In a hypothetical state of perfect competition, where Pepsi and Coke are perfect substitutes and customers have no loyalty, and with constant or declining marginal costs at scale, Coke increasing their profit margin by 1% without Pepsi doing the same would result in Pepsi eventually taking the entire market from them. And if they both raise margins, that should result in a third party taking the entire market. Obviously this isn't as good for soda shareholders as if all soda companies raised margins at the same time, but game theory is supposed to prevent that kind of cooperation, and keep every company at their competitors' throats.
However, if both companies had enough shareholders in common -- or just one big shareholder in the Soda Index -- then they sort of stop being competitors, and just become brands.
As I said on the flip side the fact that all workers are pushing for higher salaries isn't a reflection of collusion between different sets of workers, it's just a reflection of the new economic conditions on the ground.