VA and SQ are in a codeshare and FF partnership for westbound Global Connections.
This doesn't do much to control the product luring the passengers into their product. It's a start, but remember at one stage QF had a codeshare and connection with SQ and they got ditched and moved to a middle east partner. From SQs point of view they would want a stable partner in the Australian domestic scene that they can plan long term with.
As for SQ's investment record, they are not much better than Etihad. SQ's involvement in Ansett (through a 25% stake in NZ), Virgin Atlantic (huge losses and stake subsequently sold to Delta), Tiger Airways Holdings (Parent company of Tiger Airways Australia), NokScoot Thailand (bankrupt and subsequently liquidated) and Virgin Australia 1.0 have all ended in tears.
Having significant controlling shares is the issue. SQ wanted to buy out Ansett and was blocked by AirNZ as they wanted to control the company. SQ was not allowed any board positions in its stake holding so had not much to do with Ansetts woes, the NZ gov was blocking SQ investment in turn for share increases that could have changed Ansetts fortunes earlier. The hookup with VA was in similar circumstances where SQ had very little say in the running of the business and AirNZ and Etihad controlled enough shares to make sure the partners shared traffic flow, but by having three completely different airlines in bed does not work well to provide synergy with one partner, as well as Virgin Group having its say in proceedings.
Not exactly the great investment record for what some consider the 'so called saviour' of airlines.
Nothing to do with being a 'Saviour', it's about good business. SQ needs a good partner in Australia, has the money to capitalise, and a network to major international destinations. A lot of the shuffling in Australian aviation has giant egos making decisions that make only marginal business sense. AirNZ offers an Australian partner very little. Connections to the US via NZ, when everyone is going more direct, and poor Europe and Asian connections where the business is booming.
BTW how Qantas treated Air Pacific was a good indication of how Australian airline execs do business, they were using their four board positions to veto any possibility of independent competition with the Roo. Hence why the Fiji government kicked them off the board and Fiji Airways moved forward from then.