There's some major historical events here. It's not just random movement. Here is a sort of visualization of key points and the USD share of global reserves with the events attached. The number in percent is the USD share of global reserves.

1970 (85%) - Up until 1971 [1] the USD was backed by gold by the Bretton Woods system. Other countries could trade USD in for gold at a fixed rate and in exchange would peg their currencies to the USD and trade in the USD. The idea was to prevent the US from ever being able to exploit their power in this system because if we printed too many dollars other countries could just hoover those dollars up on the cheap, convert them to gold, and make a bunch of money. Nonetheless we did print excessive amounts of money and abuse the power this system was granting us. So France dutifully hoovered up those dollars and made a gold call. We said 'nah', defaulted on our debts, and withdrew from Bretton Woods. This led to the famous quote from Nixon's Secretary of the Treasury: "The dollar is our currency, but it's your problem."

1990 (47%) - Following those events, the USD began seeing rapid inflation, and other countries were rapidly dropping the dollar. This 'peaked' around 1990. But then in 1991 the USSR collapsed. This not only left the US as the undisputed and sole 'king' of the world, but also led to these former nations beginning to dollarize once the dust had settled. The USD suddenly again starts to see mass adoption.

2001 (72%) - The adoption reaches its peak in 2001. At this point not only was there the dotcom bubble, but the world order begins clearly shifting with China and Russia developing increasingly rapidly and looking to become viable world powers once again. And there's been a gradual process of de-dollarization since then declining to where it is today to less than 57% and very much trending to where we were right before the USSR collapsed.

2025 (57%) - Where we are today. We're very much trending towards 1990, only 10 points away, which is the level when everybody was dumping the USD, the US economy was shaky at best, and there was another major superpower in the world and nobody was quite sure who would 'win.' This is far more significant than 'random noise' you're implying.

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I am leaving out plenty of relevant happenings including the transition to the petro dollar, South American economic crisis, and so on - but these only contribute to eras I think, while the above are the main drivers.

[1] - https://wtfhappenedin1971.com/

I only check the US stock markets to see the health of the US Dollar. Every time it reaches new high it means dollar devalues a tiny bit more than the last stock market peak.