It had been, for decades, illegal for one person to support one specific candidate/campaign. It was never quite enforced such that it made a huge difference (shell companies, PACs, etc make it easy to skirt rules and funnel campaign support) and candidates get progressively better at asking for "support" without actually making the tit-for-tat which moves it from the "lobbying" arena to "bribery".

Also, IIRC that ruling established the precedent needed for SuperPACs and moved the individual contribution threshold.