The benefits of artificial vitamins will be if you do not receive natural vitamins from food.
And it does not have to be a serious vitamin deficiency - vitamin deficiency in a fully-fledged diversified person normally cannot be. But there is also hypovitaminosis and they are already much more common. For example, 70% of the population is deficient in vitamin D in Russia. And the deficiency of vitamin B12 - up to 16% of the population.
It is possible to compensate for hypovitaminosis with the help of artificial vitamins.
Yes, but not much of it. To reap the obvious benefits of vitamin supplementation, you must be vitamin deficient. And the difference between a molecule formed in an apple, and the same exactly, but from the plant, does not exist.
In short, artificial vitamins are no different from natural ones.
I suggest you read an interesting article on this topic:
Vitamins: natural vs. synthetic? - Articles - CMT: Scientific Approach