It’s funny - he implicitly addresses this in the previous paragraph. Here’s the full quote. Pages 11-12:

Putting the fall of communism at the center of the story of neoliberalism’s rise requires an understanding of the role of communism in shaping the politics of the United States in the sixty years prior the to 1990s that is different from what is offered in many histories. In these accounts, fear of communism is treated as a limiting force on progressive politics. Countless progressive movements, it has been argued, trimmed their political sails rather than risk being tagged with the kiss-of-death label, “soft on communism.” But the threat of communism, I argue, actually worked in a quite different direction: It inclined capitalist elites to compromise so as to avert the worst. American labor was strongest when the threat of communism was greatest. The apogee of America’s welfare state, with all its limitations, was coterminous with the height of the Cold War. The dismantling of the welfare state and the labor movement, meanwhile, marched in tandem with communism’s collapse.

To argue for communism’s importance is not meant to rehabilitate it as a political movement. Communism was an indefensible system of tyranny. Rather, it is meant to help up to understand the role that communism played in the century when it was a feared force, and then to call on us to reckon with the effects of its sudden and complete disappearance from international and national affairs . . .