Primary reason imo was 70-0 after 5 overs, whether chasing 350 in 50 overs or 300 in 43, I don't think it would have made much difference thereafter, from that point NZ had a control SA never quite managed to wrestle away. You can blame the SA team or simply tip your hats to Brendon McCullum and say sometimes there's not a lot, or even nothing, you can do different to change things, you just have to accept someone played a blinder and say well done to them.