The world gave the illusion of loving a dollar, by storing up "promises of more dollars later". But the dollars themselves? No, they were largely sent right back where they came from — the US Treasury department — in exchange for an investment product that would return those same dollars, plus a few extras along the way in interest (AKA "US Treasury bonds" — "more dollars, later"). The US Treasury then got to spend the returned dollars over and over and over again, as the world just kept on sending them back in exchange for more promises. So that is how it famously came to be that "deficits didn't matter". They didn't, just as long as nobody stopped and considered the future.
So with this perspective, we can readily see that the world didn't assemble a trillions-of-dollars warchest of US dollars, because they just love a dollar, but they got rid of trillions of dollars because they didn't really want them after all. They wanted to "be able to say they had trillions of dollars", only because this gave credibility to their own currencies, and to grow their own economies. But aside from these bragging rights to "a massive stack of dollars that are due to them some day", they had no real use. It's not like the US would simply allow the rest of the world to buy up everything in the good old US of A and we'd own it all lock stock and barrel, in exchange for all these dollars we have that, on paper, say we could buy it all many times over now, is it? It's clear that is not allowed — America buys up the rest of the world, not the other way around! Anyway, I digress... Let's get back to the world and it's love for a dollar...
Today (since 2007 when the global financial crisis started to erupt) the problem is that the world actually has fallen out of love with the idea of "more dollars later". There was a realisation that there were fewer than a Trillion dollars in existence in 2007 (the US monetary base) and many, many times that amount was already owed to people all over the world in many different ways and from many different entities, but not least by the US Treasury department. The world appears to have stopped investing in the future of the US economy and long term debt investment products, and has instead switched to demanding actual dollars or very short term Treasury investment products, such as 13-week Treasury bills (when the "yield" on a bond goes down, this means the price has gone up - i.e.: that there is great demand to buy them... As we can see, at the moment there is insatiable demand for 3 month Treasury bills; which are "as close to cash as you can get without physically stuffing it into a shoebox under your bed"... which is not something that the world's national Central Banks are in the habit of doing of course).
The world finally does actually love a dollar, rather than a long term debt asset that promises more dollars later. It turns out, the world loving the dollar isn't such a good thing for America ... or any of the other countries that have built up massive levels of debt in the good times of the past. They can't pay all the debts with the amount of base money available within the system today. So, do you think there might be only one realistic way to pay all these debts, without the system collapsing and probable breakout of another world war?
Perhaps it would be better to ask where all the love came from and then left?