The change was originally discussed here:
Why is Area 51 proposal for Database renamed to Database Administrators?
Essentially, "Databases" isn't terribly clear name for a site. It is used by many professional disciplines. So we had to become absolutely crystal clear about the primary audience for this site. Ideally, a clearer title could have be chosen early on, but before launching the site, a choice had to be made.
Our choice came down to either closing it as a duplicate of Stack Overflow and Server Fault
to clarify the proposal as a site for "Database Administrators"… a site for professionals who properly call themselves "DBAs" as a full-time profession; Those who identify themselves as neither programmers nor system administrators and don't currently feel they have a place on our network.
So we renamed "databases" to DBAs before launch rather than leaving the target audience to chance, and later having to close it down when 70-80% of the content duplicated existing sites.