(CNN) The death of David Koch on Friday -- and the broader retreat he and his brother made from politics since the 2016 election -- brings an end (if not the end) to one of the most influential (and controversial) chapters in modern American politics. Like them or hate them -- and almost no one feels indifferently about David and Charles Koch -- it's impossible to overlook the impact they have had on our current political culture.

Prior to the Koch brothers' entrance into the political space, which began in a major and concerted way with the founding of Americans for Prosperity in 2004, most outside groups were the equivalent of pop-up stores. They'd emerge from nowhere during the heat of an election -- usually a presidential one -- spend millions of dollars (from a handful of wealthy donors) and then disappear. From one election to the next, there was very little continuity in these groups and, as importantly, no repository for data collected or lessons learned.

What David and Charles Koch did starting in the mid-2000s was the equivalent of building not just one permanent store but an entire block of them. In this, they were helped -- mightily -- by the Citizens United Supreme Court ruling in 2010 that allowed political actors like them to spend more freely on efforts to directly advocate for their preferred policies and politics.

Rather than throwing their considerable wealth -- they are both billionaires -- at fly-by-night political operations, they built their own from scratch, with an eye not toward short-term gains but to affecting longer-term changes in the culture. So, it wasn't just a single quasi-political organization. There were think tanks to incubate libertarian ideas that the Koch favored. There were various foundations to influence public policy outside of the context of campaigns. It was a one-stop political and policy shop, a sort of shadow Republican Party but crafted in the libertarian molds of the Kochs and entirely controlled by them.

That wasn't the only thing that the Koch brothers did differently. While most outside groups up until Americans for Prosperity's formation had dumped all the money they raised into TV ads, the Koch brothers instead focused far more on building grassroots infrastructures -- focusing, again, on sustainability rather than immediate success. By the 2016 election, Americans for Prosperity had state directors in 34 states, according to the New Yorker's Jane Mayer