I agree with the assessments by both Sal Paradise & Skyeterrier.
On reading the account, I, too, wondered whether the companionway had been left open--the volume of water that got into the cabin seemed large in a very short time. There were experienced sailors, though, so I'd be surprised if they'd done so.
Age makes a difference. The account mentioned that they were rotating on 1 hr watches. That's very little time for rest, but a 1 hr watch might have been the best that they could do. Younger folks might have tolerated longer watches, then recovered better between watches.
The wife appears to have been a bit disoriented and misfocused after the hit; in contrast, the husband, despite his injuries--and I wouldn't be a bit surprised if he wasn't concussed given the impact force to his head--seems to have retained excellent situational awareness.
It didn't sound like the boat was sinking or taking on additional water, but from what I could piece from the story the hypothermia and overall condition of the two and the loss of life raft and effective communications, along with the ongoing sea state, meant the situation was pretty dicey and no room whatsoever for bad luck or error. So the evacuation, while no doubt a gut wrenching decision, seemed warranted.
But added to this--the steering pedestal was apparently broken by the impact of the hit from the husband. If this actually occurred, then they were at risk of losing their ability to steer, at any moment, without additional warning.
It's easy to look at a story like this and say the boat wasn't sinking, they could have solved this problem this way, that problem that way, etc. Maybe a crew of 3 or 4 young fit resilient adults would have had more capacity to do so. I think the husband correctly assessed the situation in its totality, not just its parts, and kept his priorities straight. The sea will always be there, and you can buy another boat.