AFAIK, an important reason eunuchs were preferred as generals and high officials is because a person who was castrated or had any other deformity could not be

AFAIK, an important reason eunuchs were preferred as generals and high officials is because a person who was castrated or had any other deformity could not be emperor (https://en.wikipedia.org/wiki/Political_mutilation_in_Byzantine_culture https://en.wikipedia.org/wiki/Political_mutilation_in_Byzant...) Exceptions did occur, e.g. Justinian II, but rare. It was also common practice to castrate sons of deposed emperors.