This isn't a healthy young man with a few grazes. This is an elderly stroke survivor who has no doubt been traumatised by the shock of finding the floor disappearing from beneath him.
I've had a few broken bones in my life. In my 30s, I shrugged it off and got back to work as soon as I had the cast on. Now that I'm in my 60s, any kind of fall is a bit harder to deal with.
As I've said upthread, my late husband was a stroke survivor. Prior to the stroke, he'd shrug off serious injuries. (He was in manual work for many years before becoming a teacher. On one memorable occasion, he finished up with boot full of blood as a result of an axe going into his leg when he was working in forestry.)
He was in his early 70s when he had his stroke. Everything became much harder after that. As a doctor explained to me, once you've had a stroke you're much more vulnerable. Never mind the life-changing brain injury and physical weaknesses that you're left with - any time you have a subsequent illness or injury, you can find that the stroke victim's original stroke symptoms reassert themselves.
For example, my husband had to learn to walk again. In the immediate aftermath of the stroke, his hemiparesis meant that he couldn't even sit up. Any time he was unwell, the initial stroke weakness could return and an injury which at one time he would have ignored would be to his severe detriment.
In the case of the OP's husband, the floor literally gave way from beneath him. In a stroke survivor who knows that he can no longer trust his body, the shock impact must be severe.