HBO ran off the road when Chris Albrecht left due to personal issues. They broadcast s e x and the City, Sopranos, Six Feet Under, Deadwood, The Wire, Band of Brothers, Entourage, etc. under him. The MM and BB decisions were made by his successors. They've got a really solid team in place now, with a great pipeline full of projects like True Detective.
"Difficult Men" by Brett Martin is an interesting read about the creation of those shows. (David Chase and Matthew Weiner really live up to the title).
BTW, Albrecht is at Starz now, where he hasn't been able to replicate his HBO success.