If a relilgious group were to pour tons of money toward electing a Senator, that would be blasted as a blatant violation of the much-venerated "separation of church and state." It would be widely scorned as contrary to the first amendment of the Constitution which in essence struck a deal. You, religion, stay out of politics and we, government, favor no religion over another.
Until yesterday, the rough equivalent of that dividing line kept giant corporations from bankrolling political candidates. The Supreme Court's decision now allow the country's goliaths to spend whatever they want on politicians and parties that offer them the best deal. Favoritism, the very scourge that the church-state principle tries to prevent, thus becomes a staple of the electoral process, giving the biggest and wealthiest players an overwhelming advantage. All in the ludicrous name of "free speech."
If religions were permitted to do the same, to curry privileges by courting public figures, most of us would probably shudder until our teeth rattled. Yes, it happens even now, but to a limited degree. Imagine if the door were thrown open?