Just with pure Wikipedia-ing... Mikhail Moiseyevich Botvinnik was an assimilated Jew. Bronstein might have seemed "more Jewish" for all I know and so not have been considered desirable.
Also, terrible mistakes aren't unheard of in this level of play - I remember an account of the Karpov/Korchnoi match mentioning a few. The pressure in such a high level match is intense. Remember, no one has a day to analyze their next move. One player seals their move and it isn't revealed till the next day. True, they each get to think about the position in general but that's harder.
Also, terrible mistakes aren't unheard of in this level of play - I remember an account of the Karpov/Korchnoi match mentioning a few. The pressure in such a high level match is intense. Remember, no one has a day to analyze their next move. One player seals their move and it isn't revealed till the next day. True, they each get to think about the position in general but that's harder.