To the victor go the spoils.
After WWII the US became the reserve currency for the world. Because of that we had unprecedented wealth. For many years we were the richest country in the world, we had the best industrial base of any country, we had the best research and development, the best education system in the world. So it should not be hard to imagine that other countries would like that. China would like to be in that position but it would destroy their entire economic model. If they knocked the US out of being a reserve currency they would also lose their biggest customer. Japan used to have a great industrial base until their currency became too strong.
Europe is also no good, they have become a socialist paradise.
So then I think we would be very foolish to think that there isn't someone out there that wants what the US has. In fact, instead of having the "de facto" world currency, they want one world currency. This is what we are told in the Bible. And with modern technology of RFID chips and digital currency they could wield much more power than any dictator in world history.
There are two ways to sell this, to the power hungry sociopaths just explain how this will give them all the power and put them in total control of the world. To the useful idiots sell it because it will reduce crime and fraud. What the idiots won't understand is that you are reducing crime by redefining it. The government will become the greatest crime family in history.
That is the prize, right now there is a future megalomaniac with his eye firmly on the prize. The good news is that this guy will probably appeal to less than 5% of the world's population. Therefore in order to seize power he will have to reduce world population, say through a plague, or better yet through a bioweapon he could inject into people. He can also use famine because when people are focused on feeding themselves they can't worry about other things. I would expect to see food processing plants sabotaged, set on fire or bombed. I would also expect to see fertilizer cut off to reduce the crop yields. Also if he could disrupt the supply chain that would be awesome, so many different things will begin to break and not be serviced. Also cut back on fuel. If people don't have enough food and fuel you will have massive inflation and then they must focus solely on surviving.
Also, divide and conquer. If you represent 4% of the population you can still win if you get 45% of the population fighting 45% of the population.
So even though we have seen the patents for a digital currency on an RFID chip, before they roll out this one world currency I'd expect to see all those other signs first.