I'm studying Imagism, the "brief movement" that had its start sometime in 1912 and was "over" by 1917.
There are a few constants when I read material relating to Imagism or the Imagist poets. The first is that T.E.Hulme is its pioneering theorist. Ezra Pound, an emigree to England, produced an anthology of his friends, introduced the word "Imagiste" in reference to Hulme's poetry, and later promoted H.D. (Hilda Doolittle) as a model Imagist poet. H.D. married Richard Aldington, another of the small clan of Imagists.
But then the unthinkable occurred. A bright woman, Amy Lowell, became interested in the theories of Hulme et al, and published her thoughts. In many accounts, this activity by Lowell is connected with the conclusion of Imagism as a viable "movement." She is accused of "appropriating" Imagism.
Pound snubbed her, turned to his own theory of "Vorticism," and snidely referred to Imagism as "Amyism."
Versions of this history are repeated in account after account. And yet, in account after account, Imagism is said to be a constant influence on contemporary poetry and poets.
From The Academy of American Poets: "Though Imagism as a movement was over by 1917, the ideas about poetry embedded in the Imagist doctrine profoundly influenced free verse poets throughout the twentieth century." and : "By the time the  anthology appeared, Amy Lowell had effectively appropriated Imagism and was seen as the movement's leader. "
How can a movement come to an end and yet still be in such evidence?
It's the old, tried and true manuever of dissociation. We (the 'in' group, Pound & his cronies, white male heterosexuals ) refuse to acknowledge you (the outsider, Lowell, women with brains and no partners) as an authority. We will dissociate ourselves from you, from your ideas and refuse to acknowledge your value. The dissociation is so severe that agreeble components are (apparently) thrown out. However, it doesn't preclude a sort of underground continuation. Thus, Imagism remains alive.
Dissociation - another form of acceptable insanity. Another way to silence.