I too would like to know how Communists and Ayn Rand got to be "rational".
As far as I'm concerned they fail at the first hurdle. To me rationality is the intelligent adaptation of one's means to one's ends. But what Marxists and Randists have in common is that they are
doctrinaire about means. A Marxist wants the government to do everything, and a Randist wants the free market to do everything, and the question of whether the results of such policies will be any good is either neglected or at the most assumed as a corollary of the supposed wonderfulness of the ideology.
This strikes me as having all the cold steely rationality of a Pentacostal revival meeting. Held in a vast bowl of custard. By monkeys.