The thing is, most mods are volunteers, and this - moderating such a thing - is a time consuming gig. For something that does not pay, and - candidly - can be a less than rewarding experience, - this is a lot to ask of people.
Moreover, the atmosphere, the mood, on some social media platforms may be such as to compel those who spend their time as mods to re-assess their priorities in life; etiquette on social media is still evolving, and to ask people - irrespective of whether they receive remuneration or not - to deal with the abuse and discourtesy and disrespect that is so prevalent on much social media - for, some people seem to view the anonymity conferred by a social media platform as a licence, as permission, to say whatever they wish, and act as though they believe themselves absolved of the need to do so with any semblance of courtesy, manners, or respect - is a lot to ask of anyone.
Furthermore, very often, moderating such a platform is not just a a time consuming gig, but it may also be one where the lines of communication (between mods and admins, higher up the social media hierarchy) - and the respective powers or authority - may not be especially clear.
Above all, guidelines on what is accepted behaviour and conduct, in other words, the rules of the house, are often constantly evolving, - what one can say and how one can say it are matters of ongoing huge debate in the online world - and may not necessarily be consistently applied, or thought through, or may be constantly changing.
And some sites have capricious owners with narcissistic personalities who are easily triggered and who deeply dislike being challenged, or questioned, and who choose to arbitarily change the rules - whenever rules exist - on a whim, or whenever the mood takes them, sometimes without even having the courtesy to inform their own staff.