It's unintuitive because other fiats more fictional than the dollar and the processes is therefore non-linear

The dollar is less of a fugazi than others because the world's debt is denominated in it, making it the world reserve while other fiats are basically vanity tokens

Now project out to a world where Bitcoin is the world reserve currency, what had to happen between the former and latter state?

Fiats would fall like dominoes, not all in one-shot, so it stands to reason there would always be a "last" fiat. Obviously the last fiat would be the strongest, thus dollarization is expediting us to that state.