Oh heck, I just realized; Itch.io doesn't support games that require an executable to install very well, especially if they require elevated permissions to install. You may want to note in the description that it's in that format, or possibly provide an alternate version with the whole game in one archive.
Having played many RPGM games in my life, I would make an educated guess that the reason it's packed as an executable is that it requires the RPGM'03 RTP, right? In that case, they have the RTPs as installables on the RPGM official site nowadays. You can have one version of the RTP and play as many games as you want that require (that version of) the RTP. Here's a link to the download site if you don't know what I'm talking about. It explains the pros and cons of having the RTP bundled and having it not bundled.
All in all, if people are afraid of running .exes, an .exe from a Official Site(tm) would probably be more reassuring. Plus having it in an archive lets one play the game by launching it through the Itch.io app (technically I use Playsite, which lets you manage libraries from multiple platforms like Steam and Itch.io as well as custom games, but it would be so much easier to just, merge this game's path and description and banner and everything from Itch. It's complicated stuff haha.) So uh, yeah, feel free to ignore this, but I thought I'd try to explain stuff, since it seems like you may be new to itch.io.