Why were so many communist leaders so callous about the lives of workers?
It seems like they cared more about trying to create a productive developed society than the people that society would actually be created for.
in the mid 20th century the meta-game of geopolitics was to keep the periphery under-developed and overexploited so it could be used for cheap labor andnatural resources, but would not rapidly develop enough to become a military or economic competitor with the core. The bourgeoisie learned from the mistake they made with Japan and didn't want anymore "backwards" countries catching up too fast. This led to the communist and nationalist leaders of the mid 20th century peripheral nations fundamentally acting as bourgeois revolutionaries. They fulfilled the same historical role of a Cromwell, Washington, Louverture, Bolivar, or Robespierre.
Also the paradox of the phrase "communist leaders" should be palpable. Isn't the proletariat as a class supposed to liberate itself? Not follow a charismatic leader into a new and more productive form of class society?
As always, truth seekers who want to change the world become power seekers, and once power seekers get the power they are after, they can no longer be the person theyd dreamed of being, not simply because "power corrupts" but because having power carries with it an entire new set of contradictions and incentives that being powerless did not.