The credits are still the only thing showing up as an install option in the itch app. I didn't understand why, as having a zip has solved install not being available for some other games in the past when I contacted the dev.
After downloading the game outside of the app and seeing that there's two EXEs inside, I was certain that has to be the problem.
I was very curious so I looked up some info. It turns out the itch app recently added rar support, so that wasn't the problem in the first place (sorry about having outdated info in the first post).
And according to the itch site an app manifest is needed in the case of a game having more then one exe. Otherwise the itch app won't know what to do so a game won't be compatible without one.
https://docs.itch.ovh/itch/master/integrating/quickstart.html