Many have pointed out that it's awfully convenient that Alduin saved the player at the beginning, who turned out to be his enemy and kill him. But I don't think it was convenience. Many have suggested this but I haven't read for this reason. I don't think he knew we were dragonborn, or that he was trying to save us. I think he was trying to save Ulfric. In the song if the Dragonborn is this line "And the Scrolls have foretold of Black Wings in the cold, that when brothers wage war come unfurled!" For whatever reason Alduin's plan required the civil war. It may be to distract the holds or something else entirely. And killing Ulfric could halt the war too early, so he had to stop it. We just happened to be their. Which leads to the second part. Why were we there. Nobody knew we were dragonborn . . . Except the Divines. What if they used their influence to get the Dragonborn to the Imperial Ambush and possibly even made them forget?

Food for thought at least.

Thanks for reading