The written form of how people speak to signal confusion, that thing where their people go from lower to higher pitch at the end of a sentence the way they do with questions, but with statements instead.

It indicates low confidence. In this context it is because the response is an absolute hail mary wild guess.

It’s the shortened version of “he invaded Iraq, are you okay with that??” Or some variation of that.

It’s usually used in statements that put the above into question. Something like, “yeah, but X, please elaborate”.