Probably based on ignorance that the terms belong to different, independent categorizations. "Hispanic" has to do with Iberian peninsula derived culture, language, heritage, country of birth and ethnicity, not with race.
LatinX is a racial category and I think is probably used for "any miscegenation between indigeneous meso americans and whites, except 'pure white'".
Within Hispanics, there are certainly many races in addition to Latinx: Most of Mexico's leadership is White Hispanic, the racists among them will carefully deny being LatinX. Fujimori was Asian Hispanic. Not to mention White people from Spain or Portugal.
Are there non-Hispanic LatinX? I would claim that indigenous people from a remote village in Oaxaca who do not speak Spanish could reasonably be said to be LatinX but not Hispanic.