I think it would still be Hurts' job to lose even if they got Fields or Wilson. And who knows which guy the Eagles like. Would you even dare to take another NDSU QB? Lance didn't play this season (except for one game) so I doubt he's ready to step right into a starting job. There's an argument for just taking a year to see what Hurts has - they'll likely have a good draft pick next year either way - but also an argument for letting the new staff get started with two young QBs immediately.
Everything that's happened says they like Hurts though. He's also probably better-equipped than Wentz to deal with competition, given his own college history.
So the conditional pick is based on Wentz making X number of starts, nothing more?
The Eagles had no leverage really, since they couldn't plausibly say "we'll just keep him if we don't get an offer we like." Even if they did say that.
Add on Wentz's agent undoubtedly lobbying behind the scenes to be reunited with Reich and Taylor (and on a team with a better chance of success than Chicago) and there it is.