South Australia fast-tracks 100 pct renewables target to 2027, page-47

You already have an interconnector, why do you need another connecting you to a black coal state?

The NEM network is linear, closing part of a loop will add to stability and security.
Wind and solar can generate too little or too much in SA so SA can reduce curtailment and export more at times of high production and import when needed.
Also the route chosen opens up more areas for wind and solar generation for Vic and NSW.