No orchestration is needed. Managers only need to look with disdain to anyone that brings the issue.Networks and social media extend the reach of these kinds of disdain, and take these mechanisms beyond the walls of the office and organization. In the present day climate, where accusations causing outrage tend more easily to become viral, one need not be someone's manager or even have a close relationship to exercise such power of disdain. The incentive structures in social media can act as a very efficient transmission substrate for these mechanisms.
One doesn't have to look far, to see how social media amplified groupthink has short circuited professional judgement -- even in highly visible and public circumstances. In particular, forums, email lists, and social media groups of journalists can be seen to be having such effects.
So, to get a cover up you only need to do nothing.
With just a modicum of digging, this can be seen quite clearly in 2019, in the mainstream media, which is declining but still trusted by the public.
“It is difficult to get a man to understand something, when his salary depends upon his not understanding it!”
This effect is very real and very powerful. This is why we as a society should be wary of the political exclusiveness of entire professions, entire industries, and of academia. If you're surrounded only by people of like minds, you're far less likely to have your idea checked by people highly motivated to find your faults. It's only diversity of opinions which guards against groupthink.