I’m assuming your husband had a positive covid test.
Here are my various GUESSES:
Maybe the doctor thought it was a good idea to prescribe antibiotics to prevent a secondary infection, or the off chance he already has a secondary lung infection. It’s kind of an old school way of thinking, but since your husband is unvaccinated (why?) and high risk, the doctor might think do everything to prevent a chance of severe disease. Not necessarily a terrible idea.
Or, it could be the doctor thinks your husband wanted antibiotics.
Did the doctor prescribe Zithromax? Maybe the doctor is right wing and still thinks that might work.
Was your husband also given the antibody treatment or the new pills for covid?
I hope he feels better soon.