That's awful and sad; T'm sorry about that. You didn't mention age but I'm going to assume from your description "functional" but Medicare age - I'll guess late 60s/early to mid 70s, ?underlying problems, whether kidney vs. bladder vs. prostate infection, etc. This outcome if rare,but not unheard of.
Elderly and imunocompromised, can definitely succumb to UTIs and their sequelae (not to mention just hospitalization - hospitals suck and are risky even if you are young and healthy). Although females are affected much more than males for anatomical reasons, patients coming from assisted living facilities, those with high fever, blood in urine, signs of kidney infection as opposed to bladder infection or history of multiple UTI's, need to be taken very seriously. Elderly are especially vulnerable to mental status changes/delirium with UTI's that are only exacerbated with unfamiliar surroundings/procedures, i.e. change in diet, sleep patterns, in the hospital causing comcomitant problems new mental or neurological changes such sundowning, exacerbation of what may have been a mild dementia; urgency that can lead to falls/fractures and of course there are increased risks the from just being in a hospital (huge difference between "community acquired" vs hospital acquired infections), iatrogenic complications (problems from treatment or procedures), new but pre-existing problems, decreased mobility because of rules/hospital liability issues that result in DVT/clots usually addressed with prophylactic low-dose heparin or lovenox instead of assisted ambulation, medical errors etc. Unfortunately some hospitals will even intentionally sedate patients just to becausae they are difficult or to reduce their workload.
Edit: I'll never forget when I had to take my mom in to be admitted for a UTI: just about any patient who is elderly, ever had any fall EVER, any neurological history, on any medication that can cause drowsiness per PDR, etc. are labeled a fall risk with yellow band and would have to notify the nursing staff when they had to get up or use the rest room. Well my mom would ring her call bell but wasn't exactly patient with the slow staff response (over 30 minutes), nor thrilled with the bed-rails she equated to a cage/playground equipment, and the pre-set bed weight alarms that would notify staff if a patient got out of their bed (or an extra person in); causing an angry ancillary staff helper to come running in and (in inappropriate tone in this case) ordered her "To get back in bed, you can't get out of bed without a nurse" to which my mom retorted: "I'm eighty-four, I have been on this earth at least twice as long as you and have been managing to (urinate) without you for the last 80 years!" and then re-directed her irateness at the automated bed weight settings and alarms that she blamed for ratting her out which was just hilarious (forgetting she rang her call bell)... anyway even after a week in for antibiotics she needed additional time in a step-down unit to build up her strength and weight before returning home.
Especially in a male there may have been other underlying /related issues he didn't feel comfortable sharing with you including neurogenic bladders (i.e. Parkinson/MS), medications affecting smooth muscle mobility/stasis, prostate issues, catheter use all that incrase risk of UTIs, narrowed urethra from repeat UTI's, STDs, etc...11 drugs isn't hard to fathem initially - off the bat: antibiotic, probiotic, one prostrate drug, bladder muscle drug, the usual tylenol, Lovenox, benadryl for night time, maybe BP pill.
Going into the hospital in this situation is a tough call- its absolutely better to have a great PCP who can avoid the hospital because of the complications just being in the hospital, but who isn't afraid to put your loved one there when they DO need to be there. Sadly, stuff happens.