Becoming a wizard is something that Jerry must attain in order to survive in his new life, and that is living in the Marvel World. There would be a greater threat coming to earth, and he needs a way to prepare for that.
Fortunately, he was given a System that allowed him to go to the Harry Potter Universe, where he got a letter that he would be enrolling in Hogwarts.
Jerry needed to learn a lot of things from Hogwarts School of Witchcraft and Wizardry and, perhaps prevent such incoming threats in the future with the knowledge and skills that he learned from there?