armada starscream

Megatron former second in command turns into a good guy and is welcome by jetfire. Why not Thundercracker whose devotation to the decepticon cause wavers? What made the makers do that? Was it that Starscream was more likely to be accepted to autobots because of Jetfire or likely to get kill by Megatron than Thundercracker? What makes this Alexis person so special that screamer would want to save a mud planet for her? Does Megatron know about this person? Does Jetfire? Won't they be jeolous of this person gets all Screamer attention?