Cats, even well-cared-for cats, often will do things for no knowable reason, even to the cat themselves.
We've all seen it: cat is industriously licking their crotch, leg in the air; cat pauses, leg still in the air, head slightly raised, tongue out, vacant somewhat cross-eyed stare; cat is bouncing all over the house at the speed of sound, chasing invisible interdimensional gremlins.