If a third 737 Max 8 were to crash before a root cause of this crash can be determined, would you then say it's a prudent move to ground them all? What about a fourth? Fifth?
Is your position that any grounding of the planes is unjustified until the full root cause is determined, or that "only" two crashes isn't enough to justify this action?
While I would always rather understand root cause -- and it's absolutely essential to get there eventually -- the world is full of imperfect information and assumptions are sometimes all you have.
One inexplicable crash is not a case for grounding, no; otherwise the (incredibly safe) 777 would still be grounded because of MH 370.
Regarding the 737 MAX now, the prior Lion Air crash is reasonably well understood. It has exposed some fundamental weakness and questionable design choices, but the plane was still deemed safe to fly.
Thus, what we have is one unexplained crash. Why should it be grounded?
(Having said that, I'm avoiding the MAX as far as I can. But that's based already on the Lion Air crash. So, I argue that it should've been grounded after Lion Air became understood, or not at all.)
We have one unexplained crash where early reports about what happened /strongly/ match the circumstances that brought down the LionAir flight. We also have hundreds of public complaints from pilots across the United States of similar unexpected nose down behavior from 737 MAX airplanes.
Is your position that any grounding of the planes is unjustified until the full root cause is determined, or that "only" two crashes isn't enough to justify this action?
While I would always rather understand root cause -- and it's absolutely essential to get there eventually -- the world is full of imperfect information and assumptions are sometimes all you have.