In a nutshell.
Since WWWII the world has used US dollars to settle international trade, first by agreement (Bretton Woods Agreement), then by force from 1960’s on. Gadahfi, Sadam Hussein, Iran, Syria and many other have attempted to do international trade outside the dollar, and were either bombed into submission, murdered, bankrupted, or had a CIA based coup (Operation Ajax -Iran 1951) in their country.
This need for dollars to do international trade created a demand for US dollars, thus holding up it’s value. Supply and Demand. Now the rest of the world is sick of it (mass murder, destruction, and massive money printing). So they are creating alliances to use other currencies, along with oil, gold, and other goods to settle international trade. These alliances are backed by Russia and China, two foes that cannot be attacked directly, unlike Iraq, Libya, Syria, Ukraine, etc.
The effect these new alliances outside of the dollar is two fold. First of all, the demand for dollars will go down, decreasing its value. Secondly, foreign governments have literally trillions of dollars in reserve. Think of a reserve as a savings account for countries to be used when needed for international trading. As these governments move away from using the dollar for trade they will have less need to hold as much in reserve. So, they will starting spending these reserves to buy real goods, as Russia and China have already begun. This will create yet another increase in the amount of dollars in circulation, thus decreasing the value of the dollar even more.
Does this all make sense?