Even Deathstroke hadn't expected to see Sentinel Robots here.
All he knew was that Charles had shut himself away in recent years, wholeheartedly teaching the Mutant children he had gathered every skill he could at the school.
Other than Beast, the first generation of X-Men had all been lured away by Magneto. Even Raven, whom Charles had regarded as a younger sister, had followed Magneto. The little bald man of old had become a big bald man and suffered a severe blow.
However, as Charles grew older, his willpower became increasingly stronger. He once again gathered and trained a group of children, including Cyclops, Storm, and Jean Grey.
This time, their ideological education had to keep up. From the very beginning, they had to be taught that hatred should not exist between humans and Mutants. Both sides should seek a path to harmonious coexistence and not follow Magneto's path of fighting violence with violence.
Charles planned to reorganize the X-Men once the children had grown a little older. If nothing else, they at least could not let Magneto keep stirring up hatred against Mutants everywhere.
Meanwhile, Magneto, Erik, was not in the United States. After falling out with Charles, he continued to strike across the world, seeking fair treatment for Mutants.
A few years ago, he heard that Canada's Department of Defense had established a "Department G" to research some kind of Serum meant to "cure" Mutants, and that displeased him greatly.
In Erik's eyes, the Mutant Gene was a gift, the key and future path for humanity's self-development. It was not a disease, and they did not need any cure at all.
Moreover, Canada's Department G seemed to have some unclear connection with the United States' Department K, as though they shared part of their technology and research results.