The reasoning it was to not confuse with .net framework 4.x series, and since they went beyond 4.x, it’s just .net now. I believe .net core moniker was to explicitly distinguish is from framework versions.
It didn’t help the confusion at all, tch. Being a .net guy since 1.0, you just figure it out eventually
.net isn’t dead, that’s for sure. It’s not the top ecosystem, but it is pretty healthy.