Intel sold it to Micron, tho

Micron bought IM Flash after development was ceased. But they stopped selling Xpoint products before Intel stopped selling Optane.

Inten never bought it from Ovonyx, so how could they sell it?

Intel and micron licensed the 3D XPoint nonvolatile memory cell from Ovshinsky/Ovonyx, then bled them dry by delaying royalties, eventually stopping payment altogether until they went under.

Eventually someone in the know bought the husk of Ovonyx and sued Intel.