Grab is a trash company. They started off quite OK, taking care of their drivers and operational needs. Then, management graduates started to be recruited and came in, and with that their ideas they learnt in school which was wholly inappropriate for a fast response market operating in an environment like SG.
Some of their failed ideas: start cutting costs. start squeezing the drivers, the very people that make money for them. start being uppity and trying to place themselves as the creme of private transport, when in fact it is just a convienient taxi service, start killing off competition and with that lowering their own revenues.
So the root cause of Grab sinking is the intake of non-entrepreneurial people into the organisation. I know of many drivers who complained about Grab and will from now on refuse to drive for Grab. They want Grab dead. That says how much Grab is despised in the driving community.
So if you are an investor, position yourselves for Grab's demise. Short it? Maybe timing is key.
Edit: The monetary authorities are eyeing carefully at Grab. If you were the officials in charge, would you not worry your reputation is at stake? If it gets any worse, they may pull the banking licence from Grab. Or otoh, Temasek may take it over wholesale but here is the danger....who will be competent and entrepreneurial enough to run it profitably? Any Tom Dick or Harry can run it the usual way Temasek does it...by throwing money at it.