In fairness, they were pretty accurate on the Democratic side, and Trump's entry on the GOP side threw all conventional wisdom out the window. Plus, this was very, very early on.
In still doesn't redeem how bad 538 has been since then though.
Nah, the Democratic side was sh*t too, just not as glaringly as the GOP side. Everyone besides Harry had Hillary way too low. I wouldn't necessarily object to giving Sanders straight 0s if they weren't gratuitously doling out points to people who OBVIOUSLY weren't running like Warren, Gillibrand, Cuomo, and Patrick, along with complete duds/non factors like O'Malley and Webb. At least Bernie had his cult candidate status going for him even this early, those two had squat.
Gillibrand, Patrick, etc., weren't running because Clinton was. The premise of Clinton not getting the nomination at that point was that some black swan event, like a heart attack or a massive as-yet-unknown scandal would stop Clinton from running, which would presumably result in additional people getting in the race.