Citizens United was just the inevitable outgrowth of Buckley v. Valeo 50 years ago, declaring that money == speech.

That was the wellspring of all this shit.

Supreme Court decisions are not a deterministic process like you get with code. Justices twist and contradict precedents to suit their ideological goals all the time; these days they don't even try to hide it much. The Citizens United decision wasn't something that had to happen, it was a deliberate choice by conservatives.