Yeah it's the lack of atmospheric scattering.
Also the Hasselblad camera they sent to the moon back then was actually pretty good even by modern standards.
I think it had a 7x7cm film - that's a humongous, 49cm^2 sensor compared to a regular full-frame camera, which clocks in at 8.64cm^2. As far as I can tell, the iPhone's is a tiny 0.25cm^2.
Combine with no-holds-barred lenses and you're bound to get fantastic pictures even six decades ago.
https://www.hasselblad.com/about/history/500-series/
https://www.nasa.gov/history/alsj/a11/a11-hass.html#:~:text=...
Of course, nothing can touch the light gathering ability of that Zeiss 50mm f/0.7, but then that lens wasn't very sharp anyway and modern digital sensors can go up to way higher ISO than possible with film while still making decent pictures.
- 5cm x 4cm sensor
- 150 MP
- $60k