Where was the evidence that there was anything to warn about before the incidents? Everybody trusted Boeing to have a robust battery design. Now it appears that at least some aspect of it was not robust.
I agree. Elon Musk is amazing, but I doubt he has the time to review the battery design of everything manufactured in the entire Universe so that he can warn about design flaws.
On the other hand, if your kid sticks a fork in a electrical socket, anyone can say, "you really should have bought covers for your sockets". Does that really add anything to the conversation? Sometimes the incident itself make the previously underlying flaw so apparent that the armchair commentary and criticisms (which in the Boeding case seem to obvious in retrospect to all EE professors) almost provide no real value.
Where was the evidence that there was anything to warn about before the incidents? Everybody trusted Boeing to have a robust battery design. Now it appears that at least some aspect of it was not robust.