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

The longer Max 9 has the door plug (In some configurations), and the Max 8 being shorter does not. The door plug is where the failure occurred.