Chicken and egg problem. In order to ban political contributions, you would need to elect enough polititans who will vote for that against the corporate interests mentioned. Not just a majority if polititians either.
Because the high court has decided that political contributions are “speech”, it would take a constitutional amendment to end them. That means 2/3 of both the upper and lower houses. Then, it has to get a majority in 3/4 of the state legislatures as well before actually taking effect.
For reference, in the last 41 years it hasn’t been possible to do that for an amendment saying women have the same rights as men, something that runs into far less corporate opposition than ending bribery political contributions.