Nobody believed the stranger that fell out of the sky. They could see with their own eyes the make of his ship, and his outfit made his true identity as obvious as the nose on his face.
A full-scale invasion was inevitable. While facing the brunt of Frieza’s power was impossible, they could at least make those pirates think twice about taking Yadrat.
They decided to teach the Saiyan their secret technique. Meanwhile, he’d become an unwitting carrier of their other secret, and then take it back to his masters.
By the time he displayed symptoms, it’d be too late.
Unnecessarily Long and Tiresome Authoress’ Notes:
Because a virus that causes a debilitating heart attack in a freaking Saiyan can’t possibly be a disease anybody picks up by accident.