Respiratory failure due to Pneumonia.

My mother passed away last 25th April. She was diagnosed with COPD and allergic asthma 8 years before. Taking regular medicine. She was diagnosed with pneumonia second time on 16th April. Treating MD in medicine said either it's infection or pulmonary edema, gave some antibiotics. On 18th April after pulmonologist confirmation we hospitalized her to sub unit of a well known private medical college. On the day of hospitalization she was conscious, talking to us, lucid, active as well. But after hospitalization condition worsened, lost consciousness, infection worsened despite good antibiotics. We lost her on 25th April this year. How is it possible despite of antibiotics she collapsed. I know it's an emotional inquiry for a part. I can go for paid consultation if someone can guide.