Poor baby, poor parents, poor nursery staff and I feel for the medical staff too. Horrible situation to be in.
Babies can choke - everyone can - every time you put something in your mouth it’s a risk, a tiny one in most cases but a risk nonetheless. We have to eat though.
Giving finger foods or doing baby led weaning is normal from 6 months. The more practice a baby gets at it, the better they will be at moving the food around in their mouths, taking manageable pieces, gumming at it rather than sucking. Babies used to purées only will often learn to suck at food on a spoon like they suck at milk. Adults know we eat soup and bread completely differently but they are still learning. If we suck at a food and it has a lump in it it’s more likely to fly to the back of the throat and become stuck, that feels like a shock so we take a sharp intake of breath and that can be what causes choking in some cases. If a baby is expecting a purée and tries to eat it like milk as they have learned, and if an adult is in charge of putting it in their mouths it’s possible to put it in further back than the baby would have chosen for themselves. If the family was only giving fine purées at home then the nursery should have taken note of this. I hope communication improves everywhere to make sure that caregivers know what stage the babies are at. But it’s entirely normal to do baby led weaning if you want to - and even in traditional weaning finger foods at 9 months are not unusual at all.
Tragic story, I’m so sorry it happened to them.