The 64GS was one of Commodore's last gasps at trying to make some money using the 8-bit parts they still had left in stock. The whole thing was a disaster.

It wasn't based on the C64. It was a C64. Without a keyboard and some of the other ports missing. A fact that came to bite anyone who tried a C64 cartridge game that needed keyboard input.

And IIRC one of the games that came bundled with it was a game like that.

They were at least smart enough to have the BASIC startup pointer (the one that otherwise caused READY. to appear) in the ROM patched to go to a neat little graphic telling people to turn it off, plug in a game and turn it back on again.

What Commodore saved by releasing the GS, the customer ultimately paid by needing to buy games in a format more expensive than disk or tape that would run on a regular C64.

... and given the time period, lots of people were buying PCs and offloading their regular C64 hardware and a ton of games for the price of the GS and its handful of games. And that C64 would run any GS game that was likely to come out.