Color Photos of Vietnam’s My Tho Captured by an American Soldier, 1969

IIRC, Fuji came out with Fujichrome, which was a super saturated color palette, and a lot of photographers stated liking it and using it. So, Kodak had to respond with their own super saturated color film, which they called Kodachrome.

Kodak had been known for having super accurate colors in their film (outside of the whole issue around not handling well for darker colored skin), but they were losing a lot of business to the flashier Fujichrome, hence the need to respond with their own version.

On top of that, colors shift in old film, so what may have been a more natural palette may become more garish over time, although I would normally expect the reverse to be the case.