I'm not even sure this qualifies as a cover-up. It's more of a fig-leaf that provides 'deniable plausibility'[0] and enables as many people as possible to look the other way even though 'everyone knows the score'.
[0] 'Plausible Deniability' consists of making a denial plausible eg. "It is possible he really didn't know"), and relies on giving the benefit of the doubt, while 'Deniable Plausibility' consists of actions that make an affirmation seem less likely (eg. "But there was an investigation, so surely what you claim happened would have come out!").
