The difference is that these companies keep spending the money hooking up with the right people (lobbyists) that get them results. Sure the public, charitable companies, trusts, and so on could compete with them for politicians. They don't, though. So, the lobbyists getting politicians fame, fortune, and re-election are the ones that win since those are what politicians are all about. That's also why the companies lobbyists work for seem to get all this legislation that benefits them at our expense despite so many good reasons to not do that... if they worked for us.

Lobbying, if applied, should be one of first things to consider that might motivate a politician's actions. The evidence favors that it does here in the U.S. a lot. It and votes from popular/hated topics seem to drive most of political, decision making.