Because the Spurs cannot win with what they have. Everyone wants to get rid of RJ, but as well as SA drafts, Hill would have taken over at the point, Casspi would become our SF, Thompson our starting PF and take your pick of who you want at 7.... you could have traded down with Hous who wanted the 7th pick and pick up 2 other young guns to help rebiuld.
I like the move we made for Kawhi but we failed to address our front court at PF. Not that Im for the trade, just making the point SA Had a shot at getting Casspi and they rejected it.