SIA doesn't have the money to "stump up cash" for VA, as they're currently in financial trouble themselves due to the COVID-19 situation. The Singapore Government recently raised a $10B+ funded bailout, plus a $5B loan from the banks for SQ to service their day to day debts. SQ are currently losing millions per day due to the pandemic.
In addition, there's been plenty of "so-called saviour" SQ to "take over VA" articles in the past 5 years and in all cases have ended up being 'fake news'.
Also to add to that is SQ's overall dismal record at overseas investments (including 3 in Australia). Strike 1: NZ/Ansett (bankruptcy debacle), Strike 2: Tiger Airways Australia (maintenance debacles) and Strike 3:
Virgin Australia (Capacity War and CapEx losses).
Also to add to SIA's 3 failures in Australia is their 'epic fail' in their Virgin Atlantic investment in the UK, selling at a loss to DL and DL performing the recovery job over there.
Not exactly a great record for a 'so-called saviour' of VA. Time to stop treating SQ as a 'so-called saviour' of VA when their overall record has been completely dismal.