My take: at scale, "more ethical" and "less greedy" are illusions. Corporation are not people, they are systems where, to succeed at large scale, being less greedy and more ethical is detrimental. Therefore, these good corporations are filtered out. Add to this the fact that each time, you need more and more initial investment to enter a market: you need to operate in larger scale with more and more technological investments. So, as the time passes, it is also harder to have ethical corporations operating in a market.