Question about Premature baby?

i lost my premature son. He was 10 days old. He was born on 32 weeks and 3 days gestation period. He was doing very well till the 9th day. Suddenly i got a call from doctor saying tat the bay had infection. And there is a possibility of bleeding in brain. My question is. Y are babies born prematurely? Could there be doctors fault for not being to save my baby? Is it true tat babies born in 7 months are more capable me surviving? Are there chances of it happening agen? Wat should be done to prevent premature delivery? Wat was the reason for premature delivery? Only serious answers please