Selling a Cj2 (as any aircraft)in these times isn't a very sensible decision I assume....
I understood that this aircraft isn't very recent and had to go for heavy maintenance. With the current pre-owned inventory it will anyway loose a lot of value even if sold in the future because many more recent aircraft will be available. It's fine to invest maintenance in this aircraft if the owner gives up on making money out of it. Selling it today doesn't mean loosing, it all depend on the paid price, achieved utilization and financing. Only the owner knows how much this aircraft would really cost him by selling at current market value. Getting a brand new aircraft for that money isn't stupid. Manufacturers are offering very attractive deals for new buyers.
Today's brand new TBMs will depreciate less than current pre-owned ones, provide full warranty and would be much cheaper to operate than a CJ2. To me this can be a very sensible decision.
Now in regard to the single engine issue, I believe this is more of a personal decision than anything else as statistics and ICAO annex 6 are clear about it. You always can add an engine, a co-pilot or a rotor to an helicopter, you'll never be 100% safe anywhere. I prefer to be in a very reliable (and brand new) single engine aircraft than in an old and not necessarily reliable one (the risks we are facing are not limited to an engine failure).