Sadly, I think their business model is all too easy to understand... Keep down expenses and maximize profits.
Consequently, they axe their best rated (but also most expensive) shows and opt for moderate ratings but least expensive shows.
Sanctuary is a perfect example. It brings in moderate ratings and costs very little to produce because the vast majority of sets are virtual.
As for putting SGA on NBC in prime-time, you nailed it, Rocky. There's waaay too much back-story (going all the way back into SG1) to just drop it into prime-time and expect it to gain any more legs than it has on SciFi.
It's a strong, steady performer on SciFi. It'd only be a moderate (if that) performer on NBC...