Eli5: Why were the Boeing Max 9 planes immediately grounded but not the Max 8’s?

Question

I don’t understand why regulators immediately grounded the Max 9’s, but it took two Max 8 crashes before they were grounded.

In: Other

Answer 1

This failure was undoubtedly caused by a mechanical failure, so the fleet was grounded for inspections. The earlier crashes needed analysis to determine the root cause of the crash.