Both are responsible.
Corporations are not people but they are made of people. People who will do whatever it takes to make profit, which means meeting demand.
Demand is created by consumers. Without people willing to pay the corporations that do terrible things to meet their demand, the terrible things would cease to be profitable.
Both are responsible. Corporations will not stop doing bad things if bad things bring more profit. That’s why it’s on consumers to be more mindful of what bad things they are financially supporting.
The action is taken by the big guys but only because millions of little guys are paying them to do it. They don’t need to care about taking the blame if doing so still rewards them with profit.
Corporations are not democracies. They contain one very powerful person (a CEO) and a handful of slightly less powerful people (a board and/or other C-levels). Everyone else is little more than a leaf swept away by the river.
Making the statement “corporations are made of people” whitewashes the fundamentally feudal wealth-power disparity that corporations embody.