The human body isn't too good at identifying the cause of illness. Sick? Maybe it was something you ate. Better get rid of it.

But the key words are as normally as possible. Find what you can keep down, and don't eat so much as to trigger another round of vomiting. Immune responses burn extra calories, so if you're not keeping anything down, you're going to be at a fair deficit.

In nature, without science and medicine, the body just tries to do the best it can on its own, and tries to get rid of the disease before it kills you. It doesn't have a very good rate of success, but then that's just nature. Wild animals get ill and die all the time.

Not eating, or fasting, when you want to recover actually makes a lot of sense. It lets your body focus on the recovery autophagy. Not spending energy digesting food, which can be very complicated, especially when you're sick.

Keep your electrolytes up, but if you're not hungry don't eat.

You got sick by eating, clearly eating isn't going to help matters.

Your body's autonomous functions are run by a meat computer that developed a few hundred million years ago and has only added functions on top of the existing architecture in a bubblegum and string affair.

digestion is hard. have you tried drinking calories? veggie broth, protein shakes, and fruit juice are my go-to

Because your appetite is largely controlled by your gut microbes, not your own body.
And those microbes are now dead.