What does it matter? To Trump what he inheritied may have been full of problems. What is being done here is someone is cherry picking a singular aspect of a much bigger situation and claiming partisan victory. The economy, on the whole, is doing very well. There is room for improvement, just like there was much of such room under Obama too. I admit, Obama inherited a bad situation, but to Trump this may not be a great situation either. Some of his policies have taken hold, but his biggest policy that will have effect on the economy just got passed. Really not at a point we can judge Trump as an economics president yet.
By the way, my 401k is doing great since Trump took office. Is he responsible for that? I don't know... but it sure is nice for me.