- "Good news, master! We're visiting a planet of droids."
"Wait, I've already visited all the planets. Isn't the game over?"
"Oh, please, master. This game was never finished. Let's check out some of the unused dialogue files."
- ―HK-47 and the Jedi Exile
M4-78 was a planet of droids, and they don't want any of your organic filth there! They've long since taken out all the superfluous safety equipment like handrails, and without any organics around, they can generate as much radiation as they want. Plus, since their planet has been technically removed from continuity, they can do whatever they want there without affecting canon. They killed Darth Vader and Jar Jar Binks and elected R5-D4 as Emperor, and no one even minded.