While that's true, they should also know that if they fire nukes, them and their families will probably all die. If they don't, but others (in other missile sites) do, then equally they're all dead anyway. The only hope for them and their families to survive, is to not fire. And if all their colleagues also refuse, then the chances are that Putin will be removed, so their families will escape him.Putin will also be able to get at all their families. And they know it
None of it guaranteed, but I'd think they have a better chance without firing.