Thanks for the comments, everyone!
Yes, it’s a good thing Tempus is pretty incompetent and his plots are overly complex. He has too much of a sense of drama and too big an ego. Kryptonite and a gun would be so much simpler!
It would be safe for the rats now. The rats didn’t have Kryptonian organelles that could cause subspace to transition from a chaotic to an ordered state; Kara does.
Also, if Kara hadn’t been exposed to Kryptonite, she would have suffered the same fate as the rats. Or if Clark had arrived before Kara and Tempus. It’s only because Kara arrived drained of energy (due to Kryptonite) that Tempus’s trap failed. Tempus thought she was just bait, but by depositing her there unharmed, he allowed her organelles to deal with the problem, making that universe permanently safe.
