It's probably cheaper to manufacure.
Lest we remember that that matters now.
It's not cheaper to manufacture as the default space is 32GB so the cart that comes with RE:R1 can already hold the second game with out any extra cost, this move literally makes no sense on their part.
Nah, Switch cards come in many different sizes.
"Switch game card carts come in a variety of capacities: 1GB, 2GB, 4GB, 8GB, 16GB and 32GB. At a high level, the bigger the cart the more expensive it is" - eurogamer
Also "the larger game is the one everyone is going have to download." Is likely untrue. I assume the Switch version of RE:R will be based on the PS4/XBO versions, which was 18.6gb, while RE:R2 was only around 6.8gb.
They likely cut down the original to fit on a 16gb card to save money.