One major factor here is that Columbia kept Miles's albums in print continuously and Sony continues to. You could and can find them in just about any store/record club, etc.
Then there's the fact that for the media and thus for the general public, there's only one jazz "name" at a time (Wynton, anyone?).
Also, recording techniques had advanced by the time of the classic Miles albums so that their sound quality is acceptable to most of today's listeners. Which is not true of the greatest recordings of other great jazz names like 1940s Ellington or 20s/30s Armstrong.
For as long as I've been around, Miles has always been either the token jazz album in anyone's collection, or one of the gateway albums to the world of jazz. My parents, not otherwise jazz listeners, had Sketches of Spain and ESP(!). Kind of Blue was one of the first five jazz albums I bought back in the late 1970s, and the others were on Columbia, too: Brubeck, Mingus, Monk.
And, of course, Miles made some great records. Whether they would be as widely hailed as they are without the factors mentioned above and throughout this thread, is another matter.