In fact it is. Starting from Jan 2021:
$45B of USDC was printed (https://coinmarketcap.com/currencies/usd-coin/), and around $55B in usdt(https://coinmarketcap.com/currencies/tether/). Total $100B. While m2 money suppply of USD pumped from $19.4T to $21.8t - $2 400B
https://fred.stlouisfed.org/series/M2SL
So only 4% of newly printed money went to stable coins. Assuming that none on existing USD were converted into stable coins (which is not correct)
And thats USD only. Other countries were printing too. for example ECB.
So OP is wrong. Only small fraction was converted to USDC and USDT.