For a democracy to remain functional, political elites—elected officials, judges, political appointees, and bureaucrats—must behave as though (a) they are being watched and (b) if they betray the public trust, they will face negative consequences. Otherwise there is little to prevent outright corruption. If political elites behave as though there is no cost to outright lying or procedural hypocrisy, then preventing the slide into corruption is a Sisyphean task.
The indirect effect of rampant online disinformation and propaganda, then, is that it undermines the myth of the attentive public. If the news is all “fake,” then there is no need to answer reporters’ questions honestly. If the public is made up of easily-duped partisans, then there is no need to take difficult votes. If the public simply doesn’t pay attention to policymaking, then there is no reason to sacrifice short-term partisan gains for the public good.