I think I get your point: at the end of BHM, the establishment can proclaim "Now that BHM is over, we can get back to the real thing."

Same problem with the various "history months" here in the States.

Here is an even greater problem of omission: history in general ignores the effects of the larger events that it chronicles on the everyday lives of everyday people (what the writer Unamuno called "intrahistoria" -- https://en.wikipedia.org/wiki/Miguel_de_Unamuno#Philosophy ).