 Why do the Vegans want the humans to be involved in their political struggle?
There was even serious discussion of destroying Earth out of hand, while it is still possible. They had headed for that planet confidently and unsuspectingly, using the ion drive. Even if you could get down to the bottom of the ocean and tamper with the bomb, you would only succeed in setting it off, and that's what the Sunda had been in favor of in the first place. "The crustaceans on Sunda—the lobsterlike creatures that rule the Galaxy—are usurpers. We needed companionship among the stars, and we helped them develop to the point where, in their inferior way, they were able to reason, almost as well as we, The People, can. "For more than two million years we have waited for the opportunity for revenge.
 They think the humans can add an unexpected element to their war
 They think their numbers will even the fight  They see the humans as having a complementary skillset  They are desparate and will try anything to change their situation  They think the humans can add an unexpected element to their war