Conqueror Worm question

Hey guys, I need some clarification on the "this site" part of the card, as the "permanently" seems conflicting.

What happens to a site the worm controls after it moves to a different site? Does it lose control over the previous site because it's "this" site is now a new one? Or can it theoretically, eventually, control every site in the realm?

https://preview.redd.it/ted71g798ang1.png?width=716&format=png&auto=webp&s=f2e3a1e6910b39fa9292f8e7bff0aefc387f15b7