The guess was that the original was overwritten with the pacnew - not having it now does not mean it was not the reason.
If thats all it has different from the stock you started this thread with then it would have been missing the cachy architecture repo and multilib as well.
I dont know what these contain.
The idea was that if not manually or using the official tool (pacdiff) then maybe some utility that includes pacnews .. like some ‘upgrade all the things’ tool or something of the sort.
For a while there wasa ‘noob friendly updater script’ right here on this forum that had a weird list of pacnews it would automatically delete and ignore and another list it would automatically overwrite with the pacnews.
It has since been removed for safety but some other similar thing might be the case with this pacman.conf.