 Why were the beings readily applying for the trip to Earth?
The aliens came in every shape and form, in all colors and textures—and all of them eager for a Corrigan contract. Back in 2903, the World Congress declared Terra off-bounds for non-terrestrial beings, as an offshoot of the Terra for Terrans movement. Before then, anyone could visit Earth. After the gate clanged down, a non-terrestrial could only get onto Sol III as a specimen in a scientific collection—in short, as an exhibit in a zoo. And now, please, there are many applicants waiting—" You'd think it would be sort of humiliating to become a specimen in a zoo, but most of these races take it as an honor.
 If was their only opportunity after the Terra for Terrans movement.
 They were looking for a way to overturn Earth.  If was their only opportunity after the Terra for Terrans movement.  They were bored of their lives on their home planets.  They were hoping for handouts.