In addition to your excellent response, I would add that it is probably simplistic to use the term ‘crony’ to describe any businessman who has donated to a politician in expectation of some personal benefit. I’m sure there are various shades of motivation.
Some probably donate just to insure they remain in the good graces of the politicians who hold power, seeking nothing more than to protect their businesses interests from arbitrary government regulation, etc., just like paying protection money to the mob. Others more actively seek an improvement in their business fortunes by partnering with lawmakers to create unfair conditions that benefit themselves at the expense of their competitors and the taxpayers.
Your second paragraph is a variation of “The Devil made me do it”
It is against the law for a politician to accept money for special treatment. It is not against the law for a person to donate money to a candidate or an office holder in the hopes he will support legislation favorable to him as a businessman.