There are 2 kinds of pneumonia: Viral and Bacterial.
Antibiotics only work on Bacterial pneumonia. Antibiotics weaken your immune system, which makes it worse if you have Viral pneumonia.
He did the right thing since his pneumonia was cause by a Virus.
We don’t know for sure that he didn’t have a secondary bacterial infection in his lungs. I’ve contracted pneumonia more than once as a result of the flu, and each time it responded well to antibiotics, meaning it was bacterial and presumably a secondary effect of my lungs initially being compromised by the flu virus.