Is this really any surprise? Who does not realize they are already here. It is not like they would have a hard time getting across the border.
Heck, ten-year-olds are walking right in unnaccompanied buy an adult.
They were coming in droves when I was in college many years ago. . . . education paid for and not by the U.S.(at least that is what was inferred). I don’t think they left.