Fundamentally I think it's because in the West, both transgenderism and support for communism (whatever that means to the individual) are luxury beliefs. There is unlikely to ever be a communist revolution in the stable, democratic Western nations (though watch me jinx it now) so these peoples' beliefs will never be put to the test and they will never have to live under a communist regime.

I doubt very much whether the babushka freezing in the bread line in the harsh Soviet winter ever had the opportunity to contemplate what her pronouns were. I doubt the peasants starving to death in Chinese fields were worried about their neighbours noticing their 'queer' haircut, they were probably more worried about being denounced and persecuted.

I despise modern day communists because they're just so fucking clueless. They think that they will be the ones leading the glorious rainbow revolution of peace and love, yet if they had lived in any communist regime in history they would have been lined up and shot for their bourgeois beliefs. The working classes, the actual doing-the-work working classes, the people in whose name communist revolutions are carried out, absolutely, 100% do not have time for the pronoun games and gender feels. They are the sort of people these blue-haired soyboys denounce on Twitter for 'misgendering' and 'violence.'

These idiotic beliefs are only able to exist thanks to capitalism.