I wrote a nice semi-technical splanation why Trinitron looks sharper than RCA/triad tubes, but I forgot to enter it twice so it's gone. Reconstructed and condensed:
The guns are in the same plane. Only the proximity of the red and blue beams to the deflection coil needs to be magnetically compensated, and almost entirely in the horizontal plane.
The mask consists of vertical slots rather than holes. No vertical defocussing of the beam, and the horizontal defocussing is hidden because.......
The phosphors consist of vertical stripes rather than dots. Stripes have an inherent edge in the horizontal direction, and human vision is roughly twice as sensitive to edges in the horizontal direction. From all those centuries watching food and predators moving horizontally.
Trinitron won an Emmy for its improvement in the television image. Emmy doesn't give that many technical awards. The other big one was to Ampex for inventing videotape.
(Note to self: Remember to enter this twice.)