Just a few more thoughts on how things played out in the timeline we saw in "The Road Not Taken".
What struck me was how they insisted Isaac was pivotal in saving the Union - but I got the impression from "Identity" that it was a joint effort. Kelly and Gordon went to the Krill for help, and Yaphit got out and sent a distress signal.
Then I thought, if Ed wasn't on the Orville, neither would be Kelly and Gordon. Maybe a lesser pilot wouldn't have made it, even if someone thought of the idea?
And Yaphit could have still slithered through the ducts to send a mayday message, but Ty wouldn't have been there to help him mask the signal. Maybe the Kaylons intercepted him in this universe?
And lastly, maybe Isaac taking out the Kaylon command structure on the Orville (Primary, Secondary, and Tertiary) on the Orville, meant that the Kaylon attack force wasn't as well organised as it could have been when it hit Earth?