She'd never once, for even a single second, desired to replace their master. Even if he no longer had his horcruxes, Hermione was half-convinced he would never die. Imagining being his successor was moot at that point. Lord Voldemort would outlive them all. When the trickles of doubt plagued her and she imagined him toppling, she never saw herself taking over. Antonin? Yes, absolutely. He was the logical choice. Years of being the Dark Lord's right hand prepared him for the position. For him to admit now, even candidly to his wife, that he wanted to run could be his downfall. What if someone like Rabastan or Nott heard him say something so bold? He was being reckless to admit something so personal.