Because in the end they are both members of the Democratic Party no matter what he says, or has after his name. Their ideology is simpatico and they AND the media have been making a boogie man out of Trump. Take that and mix it with a deranged person, who probably was on psychotropic medication, you have combustion and with none of the Democrats attempts to take Trump down succeeding this lunatic became desperate and figured if you want to something done right you have to do it yourself.