Yeah, I thought that too. Vulcans established the P'Jem Temple on a colony world thousands of years ago. It kind of made sense given the millennia they had been in space longer than Humans, that they had other colonies too. But if they had to go look for one after the loss of Vulcan, either those colonies didn't exist in the new timeline, were destroyed too, or somehow were not capable of supporting 10,000 Vulcan survivors.
Well, the need it to be the homeworld so there needs to be room to grow, and recreate structures of cultural significance, as well as most Vulcans, and their future offspring, and the anticipated much higher birthrate