> because it’s already biggest(network effect)

This is exactly what is downtrending. Nations fear being sanctioned and holding on to dollars they can't use

> and most stable(military/economic might/feed back effect from being global currency)

This is also what is being questioned. There is domestic turmoil and the US economy is funky.

I'm just paraphrasing Ray Dalio's recent discussions and extensions on his dialogue on the rise and fall of nations.