They decided that barring private corporations from donating while allowing other organizations from donating was infringing on the corporations freedom of speech.
I am not sure I like the outcome either but it sure made the playing field more fair if in the wrong direction.
But ultimately, it isnt the donation cash, it is the power the politicians have. Until we take back some of the power, there is no regulation in the world that will prevent the corrupt politicians from being compensated and enriched in their campaigns.