Eunuchs are favored in the civil service because they have no partisan interest in favor of one clan or another. You rise quickly in the civil service because you are able. You discover early on that you can enrich yourself by taking bribes. Bribes are a time honored perquisite of office. You have given up your masculinity for the Empire; surely you entitled to something in return. On the other hand every bit of corruption weakens the Empire ever so slightly. What will you do?