> American companies aren't diversified in the same way because investors realized that breaking up a conglomerate maximizes the stock prices

Is Google or Amazon not at the conglomerate level yet? Is it simply because their services and products are all on the internet?

I've seen the trend go the opposite direction - conglomerates are in now, because they give you nice steady dividends and less shock when one part of the company is failing. If not for AWS, where would AMZN stock be today? I've seen no serious effort on the investor level to break up these companies, and practically none politically (fledgeling movements on the far ends of the spectrum).