Why does a command economy require a large bureaucracy?

Because of the following:
Government ownership of the means of production. In command economies, governments will own some or all of the industries producing goods and services.Government pricing and production decisions. In a command economy, production is decided by government agencies, who decide the most socially efficient goods to produce. Government agencies may also set prices or give consumers rations directly.

Sir thomas more, venerated in the catholic church as saint thomas more, was an english lawyer, social philosopher, author, statesman, and noted renaissance humanist. he was also a councillor to henry viii, and lord high chancellor of england from october 1529 to 16 may 1532. i found this information on wikipedia