There are many reasons why the public disapproves of the job Donald Trump is doing -- his temperament, his lack of government experience, his dishonesty, his attacks on Gold Star families and others, his general lack of morality, etc.
But I think the chart above shows one reason that registers importantly with most Americans. They think his policies are geared toward helping his wealthy friends -- not ordinary Americans. The tax plan he is currently pushing is a prime example of that -- a plan that gives huge cuts to corporations and the rich, but little for anyone else (and cuts for those making less than $75,000 would disappear after a few years, raising their tax obligation).
Trump supports the Republican trickle-down lie -- that giving more to the rich will be good for all Americans. The problem is that has never worked in the past, and won't work now. It will just have Trump and his rich friends laughing all the way to the bank.
Fortunately, the public is starting to see through the Republican economic lies. They are beginning to understand that giving more to the rich just helps the rich -- no one else benefits. That's why they don't see Trump's policies as helping anyone but the rich.
The chart above reflects the results of a recent Marist University Poll -- done between November 6th and 9th of a random national sample of 1,074 adults (including 850 registered voters), with a 3 point margin of error (3.4 points for registered voters).