It looks so good because it was shot in VistaVision, a format where the film is run through the camera sideways producing twice the resolution of conventional 35mm widescreen.
It's also not Technicolor in the usual sense, (a.k.a three strip) but Technicolor Labs processed the film.
There's a bit of information on the restoration of the film here:
https://www.highdefdigest.com/news/s...mandments/6201