Yeah unfortunately the log doesn't have any info on the previous failure because you installed 23.4.2 manually afterwards.
Having 2 subfolders is normal, Squirrel.Windows keeps around the previous version of the app in case something goes terribly wrong, so there's something to go back to.
I've been working on our own installer so we don't have to use Squirrel.Windows anymore, because its failures are hard to look into :(
Here's the new system (not ready yet): https://github.com/itchio/itchSetup