It is easy to look at this list and say gender and ethnicity played a role (which wouldn't be surprising particularly in that era). But five people on the list are white men. Physicists were more likely to be white men (at least in those times). So no matter what list you make of physicists, they will end up on that list. My point is, it is not possible to deduce any bias from such a list. For any coveted prize there are many well deserving people that don't get it simply because there's only one prize to be awarded per year and there's no sure and objective way to know if one who got it was indeed more deserving than the others who didn't.