The abstract below is of my doctoral dissertation, The Establishment of Malory's Le Morte d'Arthur as the Standard Text of English-Language Arthurian Legend, which is held in the Edith Garland Dupré Library at the University of Louisiana at Lafayette. It also appears in Worldcat and is available at ProQuest as an open-access document; I believe in collegiality and the dissemination of knowledge, although I do expect to be cited if you use materials I put together.
The status of Sir Thomas Malory’s Le Morte d’Arthur as the canonical iteration of Arthurian legend in English is not in question. It is, however, insufficiently examined, with past explanations for its canonicity lacking detail and glossing over social, historical, and textual circumstances. Investigation of those circumstances reveals that for seven key editions of Malory’s text—Caxton’s 1458, de Worde’s 1498 and 1529, Stansby’s 1634, Chalmers’s 1816, Haslewood’s 1816, and Southey’s 1817—a confluence of editorial and printerly social stature, social contexts amenable to the materials discussed in Malory, and paratextual features provided in the editions positioned Le Morte d’Arthur such that it could be taken up by scholars and writers engaged with Victorian neomedievalist tropes as the standard text of English-language Arthuriana.