Dak didn't jump on to a 4-12 team either.
Fact is, after all the success Smith had, the league judged him to be worth about $24M a season because of what he showed on tape. When you break it down to individual play, he's a very average starter. Dak's the same way. If you're looking at the plus sides, I'd say he's more accurate than he's given credit for, has enough arm to hit every throw, is mobile enough to legitimately threaten defenses, and does a good job of going through his progressions and not locking onto one man. If you want to look at the downsides, I'd say he has very poor anticipation, struggles against zone, has bad footwork that creates several wild misses every game, and he's not comfortable stepping up to avoid sacks. So if you sum up his skillset and compare it to the rest of the league, I'd say he's somewhere in the 15-20 range among NFL QBs.
That's what teams are looking at. It's not how many games Dak and the other 52 players on the Cowboys roster won. It's not how many Pro Bowls Dak made as the third alternate. It's what Dak the individual player can and can't do for you moving forward, and how much money is that worth to you.
And as far as the OL, Dak's protection here has never been worse than league average and has usually been better. There's a shortage of OL talent across the NFL and most teams are in pretty dire straits.