Even if it is objectively better in every way (not saying it is, only going for the most extreme end point for purposes of making a point) it is not guaranteed

Even if it is objectively better in every way (not saying it is, only going for the most extreme end point for purposes of making a point) it is not guaranteed to replace C. Too many people have invested too much time mastering C and learning to deal with its quirks to simply give it up. There may come a day where basically 0 new C projects are made. I do not think that will be in my lifetime. And I say that as someone with near 0 investment in the language but intends to get more serious about learning rust in the near future.