Microsoft don't own the kernel in that sense: anyone can write kernel drivers for windows... While there are some things that the kernel can do to protect again

Microsoft don't own the kernel in that sense: anyone can write kernel drivers for windows... While there are some things that the kernel can do to protect against a bad driver, it's not a security boundary, so ultimately bad code can cause crashes. AIUI, Microsoft actually has good tooling for validating drivers before they are deployed, but it requires that you actually run the validation...