Well, he has no idea what Zeta did - or even that he even become Prime. Sentinel kinda dropped out of the loop after coming down with a nasty case of Megatron punched a hole through him.

"Perhaps I'd better understand this with context beyond being jeered at for dying." He's probably not as bothered about that as he should be but... it hasn't happened yet. Whatever. The Nile isn't just a river in space Egypt. "As far as I know, it went right from the uprising in Kaon to a planetwide war. What happened?"

He's genuinely asking. He tries not to think too hard about the fact the desolate wasteland they're on right now is Cybertron but... you know. He'd never even conceived the planet dying in his lifetime. Lucky he's good at hiding it.