See, Cryptic didn't make that clear at all. You say the Iconian left when the planet was under attack, yet there was no indication that they were under attack.
The Iconian argued with the Dewan, left through the gate, the Dewans fliddled with the machine, then BOOM, all heck broke loose like it was the planetary disaster had begun.
well not quite. the explosions started before the iconian left, as you see them being thrown around which shows something bad is happening under their watch.
finding the tablets and knowing to look for the lore writing under the accolade list (and you have to find several as they are random) is not very clear at all. that could have been handled much better. the information should appear when you look at the tablet rather than having to hunt through your own journal to find it.
however once you read the tablets it becomes fairly clear, the reason for the crater section on new romulus is from the orbital bombardment for example.