But in the latter case, that didn't happen. In-universe, because it was specifically stated in the film that their reality was a parallel universe that branched off of the prime one. And in real life, the prime universe productions still continued (if one views DSC, PIC, LDS, PRO, and SNW as the 'prime' universe.)
TOS and TNG aren't going to be 'erased' just because someone makes a Star Trek show that isn't in continuity with them.
I agree but that would because that show would be in it's own continuity. IF the Kelvinvese movies tried to be in the Prime Universe it would need to explain how Vulcan somehow came back