It didn't used to be until Citizens United. Before that point donation to a Political Action Committee was indistinguishable from donation to a campaign, and that decision created a distinction that the rich then ruthlessly exploited to fund campaign ads and paid speakers and paid writers on social media.
Citizens United was certainly disastrous, but there were many avenues to buy political influence before it.
but now ask yourself why we got citizens united and you'll maybe see what your parent poster is saying