_lateral and longitudinal accelerations were ridiculous low in 1950's cars because of very low grip
_acceleration accounts for the change in motion
_If the change in motion(acceleration or reaction of the car) is low, then the human reaction needed to cope with it is therefore slower as well.
Well at least someone "gets it".
Ok, anyone's granny could have driven the cars of the '50s then....
No one said that, you simply don't comprehend what skill was required back then ie; not the same skill as is required now. Fangio appeared to have more of that skill than one's Grandmother.
There is a very famous onboard of Fangio in the Maserati at Modena, suggest you watch it and see that no particular fast reactions were required.
Many drivers have been invited by Benz to drive the 1955 GP W196 at demonstrations, it is said Michael Doohan took to it faster than anyone because of his being a bike racer and hence his experience and feel for low grip.