The argument I've heard is that Russian players have relatively high ping to EU servers, so are more prone to becoming frustrated and playing in a silly but fun way.

I'm not entirely sure I buy that, because the 2022 invasion of Ukraine was basically "Rush Kyiv, don't stop blyat"; an overwhelming advantage in manpower and equipment was squandered due to poor planning. Russia seems to have a very long martial tradition of just charging ahead and trying to win through sheer force of will.