Well, I've done this a couple of times. When I click on install it says "downloading" and then "installing" after the circle of "installing" completes it goes back to a normal "install" button as if I didn't installed it yet. When browsing the folder where it was downloaded to I can see a folder called "Raft" but when starting the game (.exe) in it a message appears saying "There should be 'V1.03_Raft_Win64_Data' folder next to the executable" even if there is a folder named like this next to it. Also: When I go back and open the "downloads" folder of Itch there is a "354216.zip" and a folder called "354216.zip-stage" Starting the .exe from the folder or the .exe from the extracted folder of the .zip runs the game but I when I click on any buttons they doesn't seem to work. Not even the Exit button. :/
Edit: Removing all folders and fresh-reinstalling Raft doesn't work as well. Also: When installing it multiple times Itch just creates new folders called "Raft 2, Raft3, ...".