Advice please

I was gifted a cockatiel by my husband as a sentimental gift (in memory of the one I had growing up that lived for 20 years). My husband unfortunately purchased the cockatiel from Petco (I wouldn’t have chosen a store like this but he didn’t know better). The bird has suddenly died after only 2 months with us. He was told at the time of purchase the bird was only a year old. We are heartbroken and can’t figure out why he could’ve died. He had all his necessities and I know enough to properly care for this type of bird. He didn’t appear to show signs of illness but he never quite bonded with us yet and was always very aggressive (I’m wondering if maybe he was sick all long?).

Any ideas if this is common with cockatiels purchased from chain stores (poor breeding, poor health) etc? And is it common for them to due suddenly being so young? We are just so sad and I feel like I need answers.