Your build process for Mac seems to be broken somehow.. I only develop within Unity so I can't say that I have any idea how to fix the issue, but one of the problems seems to be that the executables don't have the correct file extension. (.app) The directory structure seems to be correct on a cursory glance.. but changing the top folder to app doesn't fix the issue.. Trying it in the itch app shows that there seem to be errors upon changing the application to executable upon file download.. hope this helps..
Viewing post in Known Issues (and bug reports)
Yeah, this is at least part of the problem. The bundle that Itch downloads appears to be corrupt beyond that, but with the manual download of the .rar, I was able to replace the JRE in the bundle with a JRE download from https://www.oracle.com/technetwork/java/javase/downloads/jre8-downloads-2133155.... and it ran