Re: "Why had it taken management so long"
IMHO there's 2 approached to management.
If the job is relatively unskilled or predictable you can have a command-and-control model where the boss is in charge and treats the subordinates as resources.
However if the term members are highly skilled knowledge workers (which should be the case in most IT teams) then the management should be more of an administrative function who's responsibility is to ensure the self-organising team has a clear understanding of the priorities and removes impediments to them working at their most efficient.