Obligate carnivore means cats can't just live off of whole plant foods like rice and beans.

For example, cats famously need taurine, which is naturally found mostly in meat.

However, most cat food is already supplemented with extra taurine that was synthesized in a factory, because processing breaks down taurine. AFAIK that taurine is vegan. Wikipedia says

Synthetic taurine is obtained by the ammonolysis of isethionic acid (2-hydroxyethanesulfonic acid), which in turn is obtained from the reaction of ethylene oxide with aqueous sodium bisulfite. A direct approach involves the reaction of aziridine with sulfurous acid.

Cats being obligate carnivores means they can either eat meat or hyperprocessed industrial meat substitutes with all the nutrients of meat. Agreed that its better to just have a non-carnivore, though.

When it comes to both recombinant animal protein as well as microbial- and plant-based protein for pet food, it is important to consider that although these products offer protein (as well as other nutrients that are naturally found in plants and microbes), none of these options are sources of nutrients that can only be produced by animal cells like taurine, arachidonic acid and vitamin A/retinol–and it is precisely these animal-based nutrients that are so important to consider when thinking about the dietary requirements of carnivores, such as cats. In terms of alternative sources of such animal-based nutrients, there are only two options: synthetically manufactured, or naturally produced by cultured meat.

To make cultured meat, we take a small collection of cells from an animal and then feed those cells all the nutrients they need to grow. In our case, we’ve isolated cells from mice, the ancestral diet of cats; as well as chicken, the most common ingredient in pet food.

In making cultured meat, instead of the growing cells obtaining their nutrients via food ingested by an animal, we instead feed those cells the nutrients directly, inside of a warm vessel called a bioreactor. Bioreactors are not a new technology. In fact, most people reading this article regularly consume food and beverages that are the products of bioreactors, such as yeast to make beer and bacteria commonly known as probiotics.

We feed our cells a proprietary blend of plant-based ingredients–in fact, very similar ingredients to what would be fed to a growing farm animal, such as a chicken or cow–and in the process of growing, our animal cells metabolize those nutrients to form new nutrients that only animal cells can make.

In the end, we harvest our cells as well as all of the important animal-based nutrients they’ve manufactured, and use this meat and nutrient-rich “slurry” as a one-to-one replacement ingredient for conventional meat slurries already used by pet food manufacturers.

https://vegconomist.com/interviews/biocraft-pet-manufacturers-desperate-stable-alternative/