Perhaps this is a dumb question...but if I go onto Coinbase, or anywhere, and buy 1 USDC, how does the $1.00 USD I paid for it get into Cricles Bank account.  Audits show that Circle has 1 USD for every USDC, I'm just confused as to how that USD actually makes it from my bank account, to Circle's bank account?

Does circle decide who the fiat onramps (like Coinbase) are? And they have to buy the USDC from Circle consortium dollar for dollar?

Can someone enlighten me?