> the intelligence & character of the masses are incomparably lower than the intelligence and character of the few...
I don't think Einstein is comparing the most intelligent individuals to the least (or average) here. Certainly there are individuals who are more intelligent than the average, but I would argue not incomparably so.
I believe he's speaking about the tendency of large groups of people to act more like cattle than people. The intelligence of the mob (and the character, represented by the actions of the mob) are what I see as incomparably lower than that of an individual.
And I think this is indicated by the other shortcomings of 20th century humanity that he passes along. War isn't waged by individuals (or even groups of exclusively idiots and villains). There are a bunch of physiological and sociological variables introduced that make the output of the group stupider and less caring than the output of the individual.