Cheri Bustos won her district because it was a Democratic district. It has voted Democratic down ballot. Look at the seats which switched parties in 2016. There were a bunch in Florida and Virginia that switched due to redistricting. There were some districts that had been swing districts before, and they swung the other way in 2016. NJ-5 doesn't fit into either of those but that was a Republican district that Scott Garrett because of things he did.
There was only one district that was Romney-Clinton or Obama-Trump that flipped. That was NV-3. It was Obama-Trump and actually flipped the other way to the Democrat! There were some Romney-Clinton or Obama-Trump districts where the challenger came close, but that’s the best they did. If Romney-Clinton districts were really as vulnerable as people think, you would’ve seen a few flip in 2016. These congressmen would only be marginally vulnerable in a normal election. If there’s a wave, of course, they could be very vulnerable. What they don't mention in the article is that Donald Trump won IL-17 by less than 1 point. That's not a district Trump won by 10 or 20. Those districts aren't flipping even in a wave.