They had him at 30% at a time when most reputable media had him in single digits at best. You might not remember now, but the result of that election was a real shock.
> Being dismissive of Trump’s chances early on in the Republican primary was the biggest analytical mistake of my career, and I think I deserved a lot of blame for that.
He went on to write a whole retrospective, which is exactly what you'd want to see:
I'm fine with him[0]. I don't like the apologists who explain patronizingly that 30% odds happen 3/10 times. He gave Trump much much lower odds early on and only put it at 30 in the last few weeks.
[0] I'd say the better defense of him is: the whole model is built on polls, the pollsters stink, people should complain about pollsters, not their aggregators.