I got curious about this so I did some search on how some Dev's are able to upload bigger games that run on the itch app.
Turns out there is a tool that allows you to upload up to 30GB; it's called butler.
I'm leaving a few links bellow if you are interested!
Leafo's guide: https://itch.io/t/2872417/how-to-upload-your-game-or-project-to-itchio-with-butl...
Documentation: https://itch.io/docs/butler/
YT Tutorial: