It will be investigated, but I doubt that will add much to what I have already said, going by the investigation into the Benghazi Incident. I agree in the principle of Chain of Command responsibility, and that the buck stops with the President, but as a new President with only three days in the job, he would have been guided by his military chiefs. Can you supply any evidence at all for your Obama refusal story?
I have sympathy for the grieving father of the dead soldier, but little respect for his actions in turning a private family tragedy into a public political attack on the President. His son would not have wanted him to act this way.
Trump, rather than attacking the father as you suggest, chose to instead honour the young man who died in the service of his country. I think you are seeing this through a “Trump is Evil” reality filter, so I don’t expect you to understand how offensively wrong your second-last paragraph is.