>> Exactly! But two is not numerous!
So, we wait then? Assume it's just bad luck and wait until we have 3, 4, 5+ crashes before taking action? Meanwhile, what happens if someone you know is on a plane that crashes, there have been similar accidents from other planes from the same model but someone felt that "there wasn't enough of a trend" to investigate? How would you feel then?
Each plane crash has the potential to kill hundreds of people. It is essential that potentially serious issues are spotted, investigated and resolved as soon as possible.
This isn't anything against Boeing, when the DC-10 was first introduced and ran into issues with the cargo doors failing, they investigated straight away. Then after a second crash, the DC-10 was grounded until modifications were made. They didn't wait until half a dozen planes had crashed before taking action, and if anything the DC-10 should have been grounded after the first failure (as it was, modifications were recommended but not made mandatory until 346 people were killed on Turkish Airlines flight 981).
TLDR: You don't just shrug and ignore possible issues when hundreds of lives are at stake. You ground the plane, identify the fault and fix it before allowing flights to resume.