Does diabetes lead to sepsis after two days? was the hospitals medical procedure ain’t right?

Patient: It was one week ago when my grandfather was admitted in the hospital because he was gasping for air. He has ulcer and diabetes (he has only a small thumb-size wound at his feet) but he’s still strong. That night in the hospital ward, he was injected and was given a medicine to monitor his bp, sugar, and etc. At the second night, he was almost ready to go home and he still has his own presence of mind. After some time, he starts hallucinating, and uttering words we can no longer understand. He suddenly fell then goes in convulsion and sweats too much that’s why he was brought to the ICU and was put into cardiac arrest. After some hours (morning, 3rd day), his eyes dilated, can no longer speak, gasps for air so the doctor decided to use a ventilator and there were some tube inserted in his mouth. He still can hear us but the machine now was his only life. The doctor can’t diagnosed easily what was going on. They gave him many medicines and found out that he has many implications (sepsis, heart attack, diabetes, ulcer and blah, blah..). But I wonder sepsis and many implications?, they said the infection from his feet has infected his whole body but really it was impossible because from the previous check-up from an expensive prestigious hospital he doesn’t have that much. I can’t believe how would an old man have such when he can still ran and do carpentry from previous weeks. On the morning (4th day), the nurses checked his status and he got fine but the only problem is a bp drop. After a few hours he stopped responding, he had 3 consecutive cardiac arrest in one go but they failed.Don’t you think the medical procedures were wrong?. When they check his status, their first trial shows incomplete result so they injected that much medicine again for the 2nd trial. When the light went out, there’s no electricity for about 6-10 minutes cause there ain’t any generators in ER and ICU only!.The doctor came running from another building and the nurses, too, that time. Another additional information, whhen he was brought in the ICU, the doctor said his kidney has shutdown.What do you think?..Thank you..I’ll be really waiting for your answer..hope you could make it me understand it better..