It is sad but honestly, a lot of it is copyright/trademark laws in place in most countries outside of Japan. In Japan, there is no "fair use" there is no defense for fans to make games based on IPs owned by others.

In the USA, where I live, if a company lets an IP go long enough (no matter the area it resides) and does nothing with it, it becomes fair game as long as someone else can prove use of the IP. This happened with Hasbro MANY times with Transformers over the years, even G.I. Joe characters. Slag from the Dinobots became something else and even Shockwave had a name change for a period of time due to someone being able to take ownership of the name.

Even Sega got hit with this when they brought the Genesis out, they wanted to keep the name "Mega Drive" but a band had that name and wouldn't relinquish it. They defended their ownership.

I believe at the end of the day, this is what is happening with video games (and comic books, another area of entertainment where legal action is as common as getting coffee in the morning). Companies don't want to risk losing their ownership of a game name.

Could you imagine if Capcom lost the rights to "Resident Evil" or "Mega Man"? Or if Nintendo lost "Super Mario" or "Legend of Zelda" because a fan took advantage of leniency?

Here, they are taking money in return to access the game file (I do not know when they launched it on Itch.io) which can be construed as the same as simply running a Kickstarter for this. Locking the download behind Patreon membership will surely not help their defense if needed in the future - same for Itch.io and the "pay what you want" option.