Speculation as well and highly unlikely. Microsoft drivers can very well BSOD your machine as well, not a significant or convincing threat scenario and certainly not something that lead to certificate revocation of driver developers. There is zero quality control or review by Microsoft here. Not for their own products and not for third party ones.
That's not entirely true. Certain classes of signing keys require driver developers to put their driver through a test battery and submit the results to Microsoft.
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