What does it take to be a Business Intelligence Manager?
Well, I would say one must know the complete life cycle of data.
From the gathering of data into the OLTP system, database design, performance issues, triggers, replication, log shipping, backups, SQL knowledge, etc.
Then you would have to know about Extract, Transform and Load or ETL. And how to apply business rules, cleanse data, synchronize data, backups, etc.
Then you would have to know about Data Warehousing. Facts and Dimensions. Star and Snowflake schemas. Non Relational architecture.
Then you would have to know about Reporting. How to most efficiently extract data into useful information for customer to manage the business and look for trends.
Obviously for each of the items described above, there are numerous vendors lined up for your business and you have to know the pros - cons between each.
Then you would have to know about Project Management and phases of projects and milestones and meeting with the user community and costs associated.
Then you would have to know about actual management of people / developers / DBAs and approving vacation time, sick days, promotions, hire and fires, raises, performance reviews, ability to have dialog with senior executives and customers.
And most likely you would have some years of coding experience behind you to be an effective BI Manager.
So there you have it!