Thanks for mentioning V Systems, I had searched for that one lol. Yeah, he may simply have to tried to jump on the train of premined PoS coins at that time, seeing how much money was made with them. I see their website is still live, but indeed it doesn't really look interesting. It's still developed though.

On the other hand, Primecoin could have easily been upgraded by Primecoin whales, just like the Peercoin folks did when Sunny King slowed down his contributions. For some time, XPM was in the top 30 on Coinmarketcap, so some people probably made a lot of money with it. Indeed there seems to have been some minor deveopment, at least until 2022 or so.

All three, Primecoin, Gapcoin and Riecoin have also still websites. But Gapcoin's development was abandoned in 2021 it seems. Riecoin, in contrast seems to be alive and developed actively (last commit to Github was 3 weeks ago).