The easy explanation for why people blame him for Trump’s failures is antisemitic sentiment.
But I see a deeper reason. The desire to “give a chance to” one’s incompetent family members is at least arguably noble. In contrast, there’s nothing noble about hiring someone who called you a “deplorable” as white house deputy press secretary. That’s just incompetence. By putting the blame on Kushner, Trump’s current and former supporters can avoid facing what a horrible mistake they made.
I am willing to say that I made a horrible mistake and I’m sorry I did so.
Alexander Turok 