I doubt the worry is about the subject matter considering HBO is doing a series about the pope...
most likely it is a dollar issue, pure and simple, "Band of Brothers" was a huge hit, the "Pacific" some what less so. Is there an appetite for a third WW2 spielberg/Hanks mini-series?
The economics is also changing, HBO had the market cornered on high concept/big budget series, but now Netflix is really coming on strong and cutting into their market.
http://variety.com/2016/digital/news...ey-1201750224/