Is there an article about USDC that describes what/when the major changes happened. My understanding was that Coinbase was 1:1 dollars, and they actually had t

Is there an article about USDC that describes what/when the major changes happened. My understanding was that Coinbase was 1:1 dollars, and they actually had that money in banks, etc. Then, they ended transparency and the 1:1 peg. This is when people suspect they started getting debt to buy BTC - but this is presumably legal, right? Do they have any obligation to be transparent - being a publicly traded company?