Frankly, because he's a racist islamist demagogue who got elected on a false premise of "changing the way politics is done" - when he has undoubtedly been the most hyperpartisan liberal president this country has ever had.
And that may be the cup of tea for the far-left, the problem is he portrayed himself as a completely different person.
He did change DC, but not for the better. The country is more divided than ever and more polarized than ever. There's more racial tension than ever.
As you can see from this rant, because he was lauded with such impossible praise by many admirers at the beginning, some feel justified in holding him to this impossible standard, and blame him for whatever doesn't work out.
