A) Of course, how do you know they'll do so until you elect them?
B) Many politicians who get into office are quite busy, so they tend to trust the people they actually talk to, which are often the people at campaign fundraisers. Cronies may just be people who, conveniently, are always at fundraisers, hence are familiar to politicians.
I don't think that's proper, obviously, but easy explanations rarely capture the complexity from which corruption arises.
Not to mention that a major skill in politics is to hide who pulls your strings. It is anti-democratic for Obama not to call this kind of thing out when it happens, to speak for the citizenry rather than the industrialists. If Obama was on the customer's side at all, he would be leaking information. "Sorry guys, but the way it actually works is..."
I don't think that's proper, obviously, but easy explanations rarely capture the complexity from which corruption arises.