A mere salary man like Ainz didn't have the confidence to run an organization just by reading the reports of others. That was why he dumped the heavy responsibility of running Nazarick to the talented Albedo. If a subordinate was excellent, giving to the said subordinate free reign would be the best decision. Inept supervisors who butted in needlessly would only cause a tragedy.
And Albedo was bound tightly with the dual locks of 'loyalty' and 'love'. That was the reason Ainz could leave the Great Tomb of Nazarick in her hands.
Love, huh...