I saw a video that had a hex dump of the purported .SYS file which did the damage. Basically, the sys file was all nulls.
I've seen a couple of things which support that assertion, that the sys file was zeros.
So the official claim is that a null sys file was copied to countless Windows machines worldwide, causing airlines etc all over the world to fall over.
I don't believe a word of it.
In the unix world but also in the windows world, there is this concept that a downloadable file has a hash so that by the downloader checking the hash of his just-downloaded file against the vendor's published hash, the downloader can have some confidence that the file that he has just downloaded is legitimate. However, the hash of an all-zeros file is going to look very odd. So the person at Crowdstrike who was about to sign off the sys file for publishing would have noticed the dodgy hash.
This particular sys file has to be installed on a windows machine at a very low level (or, if you prefer, a very high level of access but I'm a programmer and to me lowest level means closest to the metal). So Microsoft's operating systems programmers do not allow any old file to replace a critically important system file without various checks. In fact I would go further and say that the OS has been written to not permit any part of itself to be replaced without passing a gauntlet of checks.
There are other things as well but without spending any further words, I do not believe that an all-zeros file replaced an existing system file without assistance from a human at one or more points in the chain.