It's easy to assign what you just described to character traits that the given people happen to have regardless of their economical stance. Yet, thinking about it a bit, being nice when poor is just a life strategy that makes sense. Not only that one's precarious situation (of any kind) attracts a lot of vulnerability, it also attracts a lot of dependency on pretty much everyone's good grace. Being anything but nice by default means undermining one's success. There is not much to gain by being hostile when poor. When one gets to be rich (in relation to others) however, the game changes. People want things and it makes sense to direct their attention and energy on other people that (ideally) do have what they want or (at least) may assist them with getting what they want. And, many people would like to cut corners and resort to dirty tricks in doing so. It's not that hard to imagine what that rich folk has to face in relation with other ambitious and not so scrupulous individuals, what a winning strategy in this case would look like, and why it makes sense to become the default behavior.