From the eterenal wisdom that is the office calendar:

Never attribute to malice that which can be adequately explained by stupidity.

A paraphrasing of which I’ve been using for years, although I’m partial to the word ‘ineptitude’ rather than stupidity.

Of course, the phrase doesn’t discount the very real possibility that both malice and stupidity are in play… For examples, see any recent press release from the Home Office.