I dunno. Who is/was lining up to fight anyone?
What we generally see is there's always people willing to fight anyone. Cory Sandhagen has been calling out Usman Nurmagomedov recently. The narrative that nobody ever wants to fight x, y or z is just an angle, it's not real. Some guy from Kazakhstan is perfectly happy to fight Usman on short notice, it's not like he's some terror everyone is hiding behind the sofa from. He's a good fighter, good fighters get fights all the time.
If nobody ever wanted to fight Islam or Usman or Khabib how do they amass these win streaks? Because they've fought so many times it's pretty clear loads of people will fight them - even on short notice.