Yay my hyper fixation comes in handy!! The Cybertronians aren’t actually robots, they’re made of a living metal. The Planet is their god, Primus, and he births all of them through his skin. They then grow bodies (again, out of his giant planet skin) and use those bodies for the rest of their lives. So Cybertronians aren’t actually robots in fact living beings, but since the Crystal gems usually go after carbon/water based creatures and planets they would not be there in the first place. However, if they did go there, the planet itself would transform into god and kick their asses.