Ironically, I think these turn of the century capitalists-turned-philantropists became generous because they had so much wealth and power.

Nowadays, large companies are almost always publicly traded, meaning anyone can buy shares of the company in the stock market and share in the company's success. However, going public makes the company legally obligated (search: fiduciary responsibility) to work only in their shareholders interest, meaning make as much money as possible. The CEOs and executives are essentially employees who's job it is to ruthlessly seek growth at any cost. They're well paid, but they don't really have the power to distribute company money and policy for the sake of public good, because it's not their money to spend.

Back then, millionaires like Johnson, Carnegie, Ford, and Rockefeller owned majority shares in their companies. They initially worked to squeeze every penny they could to the detriment of workers safety and livelihood, but once they earned more money than they knew what to do with, these guys focused on their legacy and began paying workers better, funding arts and public works projects, and trying to leave a positive mark on the world.

People are inherently greedy, until they have more money than they can spend on themselves, then generosity becomes a way of buying popularity and respect. At some point, they said fuck it, and started plopping down carousels and music halls like some real life sim city.

I'm not excusing shitty CEO behavior or advocating for companies to remain privately held, I'm just pointing out this out a possible explanation for why things today are slightly different.