It's not unusual for high relative contributors to be let go while other workers (some good, some OK, some bad) are kept on. I've actually seen a person receive their bonus for their contribution (at a time when not everyone got a bonus) and then get their layoff notification the next day. It's not common but it's not all that rare, and people who have been around for a while are not shocked by this.
When it happens, it certainly feels like a kick in the teeth. If severance is being paid now, being laid off now could be seen as a gift in comparison to being laid off later with no severance.
But here's the thing - why is anyone sticking around a company that is obviously doomed and whose products are looking increasingly lame as time goes on? There are probably a few good reasons, e.g. hoping to get that severance package, but if someone hasn't started looking around for better employment at this point, you have to wonder whether they just feel unable to find work anywhere else.
I was there for a long long time and saw the products and quality declining as the directions from the executives and decisions on product investments got stupider and stupider. Eventually I had seen enough and it was pretty easy to get a better job with a company with a brighter future. If I can do it, anyone can do it. You have to ask yourself what is gained by staying the course.