I'm not quite sure how they pulled that off to be honest. It may have as much to do with the Eagles offence being poor as the Niners doing well.
Now that Hurts doesn't seem to want to take off running as much, he holds that offence back. You could see the difference between him and Purdy. Their stats make it look like they performed at a similar level, but most of his completions were relatively short and safe despite having ridiculous time to throw thanks to the Niners non-existent pass rush. He still overthrew some easy passes and was extremely inaccurate when he went long.
Purdy threw two interceptions because he has a gunslinger mentality (and also fumbled at the end of the first half because he tried to get more yards for a field goal try rather than getting out of bounds quickly), but also made more game-changing throws. People see him as a steady game manager type made to look good by Kyle's system. It's true that having an offensive guru as coach will help significantly, but Purdy is a boom or bust quarterback who will try things that gives Shanahan kittens.
I really can't see us taking down the Seahawks in Seattle. It's insane that we've got this far when we're down the best linebacker in the league, a top 10 DE, our Number 1 and 2 wideouts, starting the 6th and 7th different linebackers this season, etc. Now add on losing the best TE in the league and it looks like an impossible task against a team that are possibly the best in the NFL.
If we do lose next weekend as I predict, I hope the Bills win it all. Allen is a great player and their Superbowl heartbreak is well known, as Sham said above. Bears would be the next best. I'd love to see Ryans win it with the Texans, but that seems improbable.
If I was putting money on it, I'd predict Bears v Seahawks and Bills v Patriots in the Championship games, with a Bills v Seahawks Superbowl. Unfortunately I'd also have to predict that it will be a Seahawks win.